Statement of Comprehensive Income [Abstract]
Net income (loss)
Net Income (Loss) Attributable to Parent
Other comprehensive (loss) income, net of tax:
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
Pension and other postretirement plans adjustments:
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax [Abstract]
Amortization of net actuarial losses
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), Net of Tax
Amortization of prior service costs
Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), Net of Tax
Other comprehensive income
Other Comprehensive Income (Loss), Net of Tax
Comprehensive income (loss)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent
Earnings Per Share [Abstract]
Anti-dilutive shares
Anti-dilutive shares
Anti-dilutive shares
Weighted-average basic common shares outstanding
Weighted Average Number of Shares Outstanding, Basic
Potential number of shares issuable upon exercise of in-the-money stock options under the Long-term Stock Incentive Plan
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements
Average diluted common shares outstanding
Weighted Average Number of Shares Outstanding, Diluted
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation Expense [Table]
Share-based Compensation Expense [Table]
Share-based Compensation Expense [Table]
Award Type [Axis]
Award Type [Axis]
Equity Award [Domain]
Equity Award [Domain]
Employee Stock Option [Member]
Employee Stock Option [Member]
Restricted Stock [Member]
Restricted Stock [Member]
Performance Share Units [Member]
Performance Share Units [Member]
Incremental common shares attributable to performance share units.
Restricted Stock Units (RSUs) [Member]
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Expense [Line Items]
Share-based Compensation Expense [Line Items]
[Line Items] for Share-based Compensation Expense [Table]
Share-based Compensation
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost
Share-Based Compensation [Text Block]
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]
Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table]
Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table]
Plan Name [Axis]
Plan Name [Axis]
Plan Name [Domain]
Plan Name [Domain]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant-date fair value of awards granted during the period
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value
Weighted-average risk-free interest rate
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate
Weighted-average expected price volatility
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Weighted Average Volatility Rate
Expected dividend yield
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate
Expected term in years at the date of grant
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term
Fair Value Disclosures [Abstract]
Fair Value Measurements [Text Block]
Fair Value Disclosures [Text Block]
Asset Retirement Obligation [Abstract]
Asset Retirement Obligation, Current
Asset Retirement Obligation, Current
ARO Liability [Roll Forward]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO liability, Beginning Balance
Asset Retirement Obligation
Accretion
Asset Retirement Obligation, Accretion Expense
Additions
Asset Retirement Obligation, Liabilities Incurred
Liabilities settled
Asset Retirement Obligation, Liabilities Settled
ARO liability, Ending Balance
Income Statement [Abstract]
REVENUES
Revenues [Abstract]
Gas sales
Natural Gas Production Revenue
Oil sales
Oil and Condensate Revenue
NGL sales
Natural Gas Midstream Revenue
Other revenue
Gas Gathering, Transportation, Marketing and Processing Revenue
Purchased gas and oil sales
Refining and Marketing Revenue
Total Revenues
Oil and Gas Revenue
OPERATING EXPENSES
Operating Expenses [Abstract]
Purchased gas and oil expense
Refining and Marketing Costs
Lease operating expense
Oil and Gas Property, Lease Operating Expense
Gas, oil and NGL transportation and other handling costs
Shipping, Handling and Transportation Costs
Gathering and other expense
Gas Gathering, Transportation, Marketing and Processing Costs
General and administrative
General and Administrative Expense
Production and property taxes
Production Tax Expense
Depreciation, depletion and amortization
Results of Operations, Depreciation, Depletion, Amortization and Accretion
Exploration expenses
Exploration Expense
Impairment
Asset Impairment Charges
Total operating expenses
Operating Expenses
Net gain (loss) from asset sales
Gain (Loss) on Disposition of Property Plant Equipment
OPERATING INCOME (LOSS)
Operating Income (Loss)
Realized and unrealized gains (losses) on derivative contracts (See Note 7)
Gain on Derivative Instruments, Pretax
Interest and other income (expense)
Interest Income, Operating
Interest expense
Interest Expense
INCOME (LOSS) BEFORE INCOME TAXES
Results of Operations, Income before Income Taxes
Income tax (provision) benefit
Income Tax Expense (Benefit)
NET INCOME (LOSS)
Earnings per common share
Earnings Per Share, Basic
Earnings Per Share, Basic
Earnings Per Share, Diluted
Earnings Per Share, Diluted
Weighted-average common shares outstanding
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Used in basic calculation (in shares)
Used in diluted calculation (in shares)
Dividends per common share (in dollars per share)
Common Stock, Dividends, Per Share, Cash Paid
Fair Value, by Balance Sheet Grouping [Table]
Fair Value, by Balance Sheet Grouping [Table]
Oil and Gas Production Type [Axis]
Oil and Gas Production Type [Axis]
Production Type [Domain]
Production Type [Domain]
Proved Property [Member]
Proved Property [Member]
Proved Property [Member]
Balance Sheet Location [Axis]
Balance Sheet Location [Axis]
Balance Sheet Location [Domain]
Balance Sheet Location [Domain]
Long-term [Member]
Long term [Member]
Derivative contracts with maturities in excess of one year.
Short-term [Member]
Short term [Member]
Derivative contracts with maturities of one year or less.
Fair Value, Hierarchy [Axis]
Fair Value, Hierarchy [Axis]
Fair Value, Measurements, Fair Value Hierarchy [Domain]
Fair Value Hierarchy [Domain]
Level 1 [Member]
Fair Value, Inputs, Level 1 [Member]
Level 2 [Member]
Fair Value, Inputs, Level 2 [Member]
Level 3 [Member]
Fair Value, Inputs, Level 3 [Member]
Netting Adjustments [Member]
Netting Adjustments [Member]
Netting Adjustments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Impairment of Oil and Gas Properties
Impairment of Oil and Gas Properties
Financial Assets
Derivative Asset [Abstract]
Derivative Asset, Fair Value, Gross
Derivative Asset, Fair Value, Gross Asset
Net amount of derivative assets presented on condensed consolidated balance sheets
Derivative Asset, Fair Value, Amount Offset Against Collateral
Financial liabilities
Derivative Liability [Abstract]
Derivative Liability, Fair Value, Gross
Derivative Liability, Fair Value, Gross Liability
Net amount of derivative liabilities presented on condensed consolidated balance sheets
Derivative Liability, Fair Value, Amount Offset Against Collateral
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Impaired Long-Lived Assets Held and Used [Table]
Schedule of Impaired Long-Lived Assets Held and Used [Table]
Geographical [Axis]
Geographical [Axis]
Geographical [Domain]
Geographical [Domain]
Pinedale [Member]
Pinedale [Member]
Pinedale [Member]
Other Northern [Member]
Other Northern [Member]
Other Northern [Member]
Other Southern [Member]
Other Southern [Member]
Other Southern [Member]
Unproved Property [Member]
Unproved Property [Member]
Unproved Property [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impaired Long-Lived Assets Held and Used [Line Items]
Goodwill, Acquired During Period
Goodwill, Acquired During Period
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested balance at beginning of period
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number
Shares granted
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period
Shares vested
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period
Shares forfeited
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period
Unvested balance at end of period
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Weighted average grant date fair value, beginning of period
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value
Weighted average grant date fair value, grants
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value
Weighted average grant date fair value, vested
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value
Weighted average grant date fair value, forfeited
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value
Weighted average grant date fair value, end of period
Schedule of Restricted Share Unit Transactions [Abstract]
Schedule of Restricted Share Unit Transactions [Abstract]
Award Date [Axis]
Award Date [Axis]
Award Date [Domain]
Award Date [Domain]
Class of Stock [Axis]
Class of Stock [Axis]
Class of Stock [Domain]
Class of Stock [Domain]
Range [Axis]
Range [Axis]
Range [Domain]
Range [Domain]
Vesting [Axis]
Vesting [Axis]
Vesting [Domain]
Vesting [Domain]
Restructuring and Related Activities [Abstract]
Restructuring and Related Activities Disclosure [Text Block]
Restructuring and Related Activities Disclosure [Text Block]
Asset retirement obligations rollforward [Table Text Block]
Schedule of Change in Asset Retirement Obligation [Table Text Block]
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments [Table]
Schedule of Long-term Debt Instruments [Table]
Long-term Debt, Type [Axis]
Long-term Debt, Type [Axis]
Long-term Debt, Type [Domain]
Long-term Debt, Type [Domain]
Revolving Credit Facility due 2019 [Member]
Line of Credit [Member]
6.05% Senior Notes due 2016 [Member]
Senior Notes Due 2016 [Member]
Senior Notes Due 2016.
6.80% Senior Notes due 2018 [Member]
Senior Notes Due 2018 [Member]
Senior Notes Due 2018.
6.80% Senior Notes Due 2020 [Member]
Senior Notes Due 2020 [Member]
Senior Notes Due 2020.
6.875% Senior Notes Due 2021 [Member]
Senior Notes Due 2021 [Member]
Senior Notes Due 2021.
Debt Instrument [Line Items]
Debt Instrument [Line Items]
Long-term debt, interest rate (in hundredths)
Debt Instrument, Interest Rate, Stated Percentage
Maturity date of long-term debt
Debt Instrument, Maturity Date
Debt Maturity Period
Debt Maturity Period
Debt Maturity Period
Borrowing capacity
Line of Credit Facility, Current Borrowing Capacity
Weighted-average interest rate (in hundredths)
Long-term Debt, Weighted Average Interest Rate
Letters of credit outstanding
Letters of Credit Outstanding, Amount
Principal amount of senior notes outstanding
Senior Notes
Debt Instrument, Maturity Date Range, Start
Debt Instrument, Maturity Date Range, Start
Debt Instrument, Maturity Date Range, End
Debt Instrument, Maturity Date Range, End
Senior Notes, stated interest rate, minimum (in hundredths)
Debt instrument, Stated Rate Range, Minimum
Debt instrument, Stated Rate Range, Minimum
Senior Notes, stated interest rate, maximim (in hundredths)
Debt Instrument, Stated Rate Range, Maximum
Debt Instrument, Stated Rate Range, Maximum
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at beginning of period
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number
Options granted
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross
Options cancelled
Share-based Compensation Arrangement by Share-based Payment Award, Options, Other Increases (Decreases) in Period
Outstanding at end of period
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average exercise price, beginning of year
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price
Weighted average exercise price, granted in period
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price
Weighted average exercise price, canceled in period
Share-based Compensation Arrangements by Share-based Payment Award, Options, Other Share Increase (Decrease) in Period, Weighted Average Exercise Price
Weighted average exercise price, end of year
Options exercisable, shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number
Options exercisable, weighted average exercise price
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price
Unvested options, shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares
Unvested options, weighted average exercise price
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value
Weighted average remaining contractual term, options outstanding
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term
Weighted average remaining contractual term, options exercisable
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term
Weighted average remaining contractual term, options unvested
Share Based Compensation Arrangement By Share Based Payment Award Options Unvested Weighted Average Remaining Contractual Term
The weighted average period between the balance sheet date and expiration for all unvested portions of options outstanding under the plan, which may be expressed in a decimal value for number of years.
Aggregate intrinsic value, options outstanding
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value
Aggregate intrinsic value, options exercisable
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value
Aggregate intrinsic value, options unvested
Sharebased Compensation Arrangement By Sharebased Payment Award Options Unvested Intrinsic Value1
The total dollar difference between fair values of the underlying shares reserved for issuance and exercise prices of unvested portions of options outstanding and currently exercisable under the option plan as of the balance sheet date.
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]
Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]
Derivative Instruments, Gain (Loss) [Table Text Block]
Derivative Instruments, Gain (Loss) [Table Text Block]
Derivative [Table]
Derivative [Table]
Fair Value Hierarchy [Domain]
Fair Value, Inputs, Level 2 [Member]
Measurement Frequency [Axis]
Measurement Frequency [Axis]
Fair Value, Measurement Frequency [Domain]
Fair Value, Measurement Frequency [Domain]
Fair Value, Measurements, Recurring [Member]
Fair Value, Measurements, Recurring [Member]
Derivative Instrument [Axis]
Derivative Instrument [Axis]
Derivative Contract [Domain]
Derivative Contract [Domain]
Commodity Contract [Member]
Commodity Contract [Member]
Derivative [Line Items]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset
Compensation and Retirement Disclosure [Abstract]
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table]
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table]
Defined Benefit Plans and Other Postretirement Benefit Plans [Axis]
Defined Benefit Plans and Other Postretirement Benefit Plans [Axis]
Defined Benefit Plan and Other Postretirement Benefit Plan [Domain]
Defined Benefit Plan and Other Postretirement Benefit Plan [Domain]
Pension Plan [Member]
Pension Plan [Member]
Other Postretirement Benefit Plan [Member]
Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost
Defined Benefit Plan, Service Cost
Interest cost
Defined Benefit Plan, Interest Cost
Expected return on plan assets
Defined Benefit Plan, Expected Return on Plan Assets
Amortization of prior service costs
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)
Amortization of actuarial losses
Defined Benefit Plan, Amortization of Gains (Losses)
Curtailment loss
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments
Periodic expense
Defined Benefit Plan, Net Periodic Benefit Cost
Debt Outstanding [Table Text Block]
Schedule of Debt [Table Text Block]
Statement of Cash Flows [Abstract]
Statement [Table]
Statement [Table]
Scenario [Axis]
Scenario [Axis]
Scenario, Unspecified [Domain]
Scenario, Unspecified [Domain]
Statement [Line Items]
Statement [Line Items]
OPERATING ACTIVITIES
Net Cash Provided by (Used in) Operating Activities [Abstract]
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Depreciation, depletion and amortization
Depreciation, Depletion and Amortization
Deferred income taxes
Deferred Income Tax Expense (Benefit)
Share-based compensation
Share-based Compensation
Other Operating Activities, Curtailment Loss
Other Operating Activities, Curtailment Loss
Other Operating Activities, Curtailment Loss
Amortization of debt issuance costs and discounts
Amortization of Debt Issuance Costs and Discounts
Net (gain) loss from asset sales
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property
Unrealized (gains) losses on marketable securities
Marketable Securities, Unrealized Gain (Loss), Excluding Other than Temporary Impairments
Unrealized (gains) losses on derivative contracts
Unrealized Gain (Loss) on Derivatives
Changes in operating assets and liabilities
Increase (Decrease) in Operating Capital
Net Cash Provided by (Used in) Operating Activities
Net Cash Provided by (Used in) Operating Activities, Continuing Operations
INVESTING ACTIVITIES
Net Cash Provided by (Used in) Investing Activities [Abstract]
Property acquisitions
Payments to Acquire Oil and Gas Property
Acquisition Deposit Held In Escrow
Acquisition Deposit Held In Escrow
acquisition deposit held in escrow
Property, plant and equipment, including dry exploratory well expense
Payments to Acquire Oil and Gas Equipment
Proceeds from disposition of assets
Proceeds from Sale of Oil and Gas Property and Equipment
Net Cash Provided by (Used in) Investing Activities
Net Cash Provided by (Used in) Investing Activities, Continuing Operations
FINANCING ACTIVITIES
Net Cash Provided by (Used in) Financing Activities [Abstract]
Checks outstanding in excess of cash balances
Increase (Decrease) in Outstanding Checks, Financing Activities
Treasury stock repurchases
Payments for Repurchase of Common Stock
Other capital contributions
Proceeds from Other Equity
Dividends paid
Payments of Ordinary Dividends, Common Stock
Proceeds from issuance of common stock, net
Proceeds from Issuance of Common Stock
Excess tax (provision) benefit on share-based compensation
Excess tax (provision) benefit on share-based compensation
Excess tax (provision) benefit on share-based compensation
Net Cash Provided by (Used in) Financing Activities
Net Cash Provided by (Used in) Financing Activities, Continuing Operations
Change in cash and cash equivalents
Cash and Cash Equivalents, Period Increase (Decrease)
Beginning cash and cash equivalents
Cash and Cash Equivalents, at Carrying Value
Ending cash and cash equivalents
Supplemental Disclosures:
Supplemental Cash Flow Elements [Abstract]
Cash paid for interest, net of capitalized interest
Interest Paid, Net
Cash paid for income taxes
Income Taxes Paid, Net
Non-cash Investing Activities
Noncash Investing and Financing Items [Abstract]
Change in capital expenditure accruals and other non-cash adjustments
Capital Expenditures Incurred but Not yet Paid
Fair Value Measurements, Recurring and Nonrecurring [Table]
Fair Value Measurements, Recurring and Nonrecurring [Table]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of financial assets and liabilities [Table Text Block]
Fair Value Measurements, Recurring and Nonrecurring [Table Text Block]
Fair value and related carrying amount of certain financial instruments [Table Text Block]
Fair Value, by Balance Sheet Grouping [Table Text Block]
Statement of Financial Position [Abstract]
Condensed Balance Sheet Statements, Captions [Line Items]
Condensed Balance Sheet Statements, Captions [Line Items]
ASSETS
Assets [Abstract]
Current Assets
Assets, Current [Abstract]
Cash and cash equivalents
Accounts receivable, net
Accounts Receivable, Net, Current
Income tax receivable
Income Taxes Receivable, Current
Fair value of derivative contracts
Derivative Instruments and Hedges, Assets
Gas, oil and NGL inventories at lower of average cost or market
Energy Related Inventory
Prepaid expenses and other
Prepaid Expense and Other Assets, Current
Total Current Assets
Assets, Current
Property, Plant and Equipment (successful efforts method for oil and gas properties)
Oil and Gas Property, Successful Effort Method, Net [Abstract]
Property, Plant and Equipment (successful efforts method for gas and oil properties)
Property, Plant and Equipment, Net [Abstract]
Proved properties
Proved Oil and Gas Property, Successful Effort Method
Unproved properties
Unproved Oil and Gas Property, Successful Effort Method
Marketing and other
Property, Plant and Equipment, Other, Gross
Material and supplies
Inventory, Drilling, Noncurrent
Total Property, Plant and Equipment
Property, Plant and Equipment, Gross
Less Accumulated Depreciation, Depletion and Amortization
Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion Amortization and Impairment [Abstract]
Less Accumulated Depreciation, Depletion and Amortization
Depreciation, Depletion and Amortization, Nonproduction [Abstract]
Exploration and production
Oil and Gas Property, Successful Effort Method, Accumulated Depreciation, Depletion and Amortization
Marketing and other
Property, Plant and Equipment, Other, Accumulated Depreciation
Total Accumulated Depreciation, Depletion and Amortization
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment
Net Property, Plant and Equipment
Property, Plant and Equipment, Net
Fair value of derivative contracts
Derivative Instruments and Hedges, Noncurrent
Other noncurrent assets
Other Assets, Noncurrent
TOTAL ASSETS
Assets
LIABILITIES AND EQUITY
Liabilities and Equity [Abstract]
Current Liabilities
Liabilities, Current [Abstract]
Checks outstanding in excess of cash balances
Bank Overdrafts
Accounts payable and accrued expenses
Accounts Payable and Accrued Liabilities, Current
Production and property taxes
Accrual for Taxes Other than Income Taxes, Current
Interest payable
Interest Payable, Current
Fair value of derivative contracts
Derivative Liability, Current
Deferred income taxes
Deferred Tax Liabilities, Net, Current
Current portion of long-term debt
Long-term Debt, Current Maturities
Total Current Liabilities
Liabilities, Current
Long-term debt
Long-term Debt, Excluding Current Maturities
Deferred income taxes
Deferred Tax Liabilities, Net, Noncurrent
Asset retirement obligations
Asset Retirement Obligations, Noncurrent
Fair value of derivative contracts
Derivative Liability, Noncurrent
Other long-term liabilities
Other Liabilities, Noncurrent
Commitments and contingencies (Note 10)
Commitments and Contingencies
EQUITY
Stockholders' Equity Attributable to Parent [Abstract]
Common stock – par value $0.01 per share; 500.0 million shares authorized; 240.6 million and 177.3 million shares issued, respectively
Common Stock, Value, Issued
Treasury stock – 1.0 million and 0.5 million shares, respectively
Treasury Stock, Value
Additional paid-in capital
Additional Paid in Capital, Common Stock
Retained earnings
Retained Earnings (Accumulated Deficit)
Accumulated other comprehensive income (loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax
Total Shareholders' Equity
Stockholders' Equity Attributable to Parent
TOTAL LIABILITIES AND EQUITY
Liabilities and Equity
Equity [Abstract]
Equity [Abstract]
Derivative Instruments and Hedging Activities Disclosure [Text Block]
Derivative Instruments and Hedging Activities Disclosure [Text Block]
Derivative Instrument Contract Type [Axis]
Derivative Instrument Contract Type [Axis]
Information by name that identifies a derivative or a group of derivatives by (derivative) contract risk type.
Derivative Instrument Contract Type [Domain]
Derivative Instrument Contract Type [Domain]
The name that identifies a derivative or a group of derivatives, on a disaggregated basis, by contract risk type.
Oil derivative contracts [Member]
Oil derivative contracts [Member]
Derivative instrument whose primary underlying risk is tied to commodity prices.
Natural gas derivative contracts [Member]
Natural gas derivative contracts [Member]
Derivative instrument whose primary underlying risk is tied to commodity prices.
Production [Member]
Production [Member]
Production [Member]
Storage [Member]
Storage [Member]
Storage [Member]
Income Statement Location [Axis]
Income Statement Location [Axis]
Income Statement Location [Domain]
Income Statement Location [Domain]
Realized gain (loss) on commodity derivative contracts not designated as hedging instruments
Realized gain (loss) on commodity derivative contracts not designated as hedging instruments
Represents the realized gain (loss) on commodity derivative contracts not designated as hedging instruments for the period.
Unrealized gain (loss) on commodity derivative contracts not designated as hedging instruments
Unrealized gain (loss) on commodity derivative contracts not designated as hedging instruments
Represents the unrealized gain (loss) on commodity derivative contracts not designated as hedging instruments for the period.
Realized and Unrealized Gain (Loss) on Commodity Derivative Contracts Not Designated as Hedging Instruments
Realized and Unrealized Gain (Loss) on Commodity Derivative Contracts Not Designated as Hedging Instruments
Total Realized and Unrealized Gain (Loss) on Commodity Derivative Contracts Not Designated as Hedging Instruments
Operating Activities [Axis]
Operating Activities [Axis]
Operating Activities [Domain]
Operating Activities [Domain]
Funded Pension Plan [Member]
Funded Pension Plan [Member]
Information on funded defined benefit pension plan.
Unfunded Pension Plan [Member]
Unfunded Pension Plan [Member]
Information on unfunded defined benefit pension plan.
Pension Contributions
Pension Contributions
Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year
Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year
Other Postretirement Benefits Payments
Other Postretirement Benefits Payments
Schedule of Restructuring and Related Costs [Table]
Schedule of Restructuring and Related Costs [Table]
Segments [Axis]
Segments [Axis]
Segments [Domain]
Segments [Domain]
Denver Restructuring [Member]
Denver Restructuring [Member]
Denver Restructuring [Member]
Unrelated to Tulsa Restructuring [Member]
Other Segments [Member]
Tulsa Regional Office [Member]
Tulsa Regional Office [Member]
Tulsa Regional Office [Member]
Restructuring Type [Axis]
Restructuring Type [Axis]
Type of Restructuring [Domain]
Type of Restructuring [Domain]
One-time Termination Benefits [Member]
One-time Termination Benefits [Member]
Employee Relocation [Member]
Employee Relocation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Cost and Reserve [Line Items]
Reduction of Employees - Restructuring
Reduction of Employees - Restructuring
Reduction of Employees - Restructuring
Restructuring and Related Cost, Expected Cost
Restructuring and Related Cost, Expected Cost
Restructuring and Related Cost, Incurred Cost
Restructuring and Related Cost, Incurred Cost
Restructuring and Related Cost, Expected Cost Remaining
Restructuring and Related Cost, Expected Cost Remaining
Business Combinations [Abstract]
Schedule of Business Acquisitions, by Acquisition [Table]
Schedule of Business Acquisitions, by Acquisition [Table]
Business Acquisition [Axis]
Business Acquisition [Axis]
Business Acquisition, Acquiree [Domain]
Business Acquisition, Acquiree [Domain]
Significant Acquisitions and Disposals by Transaction [Axis]
Property, Plant and Equipment, Type [Axis]
Significant Acquisitions and Disposals, Transaction [Domain]
Property, Plant and Equipment, Type [Domain]
Permian Basin Acquisition [Member]
Permian Basin Acquisition [Member]
Permian Basin Acquisition [Member]
Williston & Permian Basins [Member]
Williston & Permian Basins [Member]
Williston & Permian Basins [Member]
Other Southern Divestiture [Member]
Other Southern Divestiture [Member]
Other Southern Divestiture [Member]
2014 Divestitures [Member]
2014 Divestitures [Member]
2014 Divestitures [Member]
Business Acquisition [Line Items]
Business Acquisition [Line Items]
Acquisition Costs, Period Cost
Acquisition Costs, Period Cost
Net Acres
Net Acres
Net Acres
Vertical Wells
Vertical Well
Vertical Well
Proceeds from Sale of Oil and Gas Property and Equipment
Gain (Loss) on Disposition of Property Plant Equipment
Schedule of Stock Issuance [Table]
Schedule of Stock Issuance [Table]
Schedule of Stock Issuance [Table]
Share Issuance [Axis]
Share Issuance [Axis]
Share Issuance [Axis]
Share Issuance - June 2016 [Domain]
Share Issuance - June 2016 [Domain]
Share Issuance - June 2016 [Domain]
Share Issuance - March 2016 [Domain]
Share Issuance - March 2016 [Domain]
Share Issuance - March 2016 [Domain]
Schedule of Stock Issuance [Line Items]
Schedule of Stock Issuance [Line Items]
[Line Items] for Schedule of Stock Issuance [Table]
Common Stock, Shares Issued in Period
Common Stock, Shares Issued in Period
Common Stock, Shares Issued in Period
Proceeds from Issuance of Common Stock
Senior Notes Due 2016 [Member]
Senior Notes Due 2018 [Member]
Senior Notes Due 2020 [Member]
Senior Notes Due 2022 [Member]
Senior Notes Due 2022 [Member]
Senior Notes Due 2022.
5.25% Senior Notes Due 2023 [Member]
5.25% Senior Notes Due 2023 [Member]
5.25% Senior Notes Due 2023 [Member]
Long-term Debt, Gross
Long-term Debt, Gross
Less unamortized discount
Debt Instrument, Unamortized Discount
Long-term debt
Long-term Debt
Less: current portion of long-term debt
Unsecured Debt, Current
Total long-term debt outstanding
Common stock, par value (in dollars per share)
Common Stock, Par or Stated Value Per Share
Common stock, shares authorized (in shares)
Common Stock, Shares Authorized
Common stock, shares issued (in shares)
Common Stock, Shares, Issued
Treasury stock (in shares)
Treasury Stock, Shares
Asset Retirement Obligations [Text Block]
Asset Retirement Obligation Disclosure [Text Block]
Components of basic and diluted shares used in EPS [Table Text Block]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]
Schedule of Error Corrections and Prior Period Adjustment Restatement [Table]
Schedule of Error Corrections and Prior Period Adjustment Restatement [Table]
Adjustments for Error Corrections [Axis]
Adjustments for Error Corrections [Axis]
Adjustments for Error Correction [Domain]
Adjustments for Error Correction [Domain]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Schedule of Error Corrections and Prior Period Adjustments [Table Text Block]
Schedule of Error Corrections and Prior Period Adjustments [Table Text Block]
Statement of Equity [Abstract]
Statement of Equity [Abstract]
Report Date [Axis]
Report Date [Axis]
Financial Statement Filing Date [Domain]
Financial Statement Filing Date [Domain]
Equity Components [Axis]
Equity Components [Axis]
Equity Component [Domain]
Equity Component [Domain]
Common Stock, Value [Member]
Common Stock, Value [Member]
Common Stock, Value [Member]
Treasury Stock [Member]
Treasury Stock [Member]
Additional Paid-in Capital [Member]
Additional Paid-in Capital [Member]
Retained Earnings [Member]
Retained Earnings [Member]
Accumulated Other Comprehensive Income (Loss) [Member]
Other Comprehensive Income (Loss) [Member]
Adjustments for New Accounting Pronouncements [Axis]
Adjustments for New Accounting Pronouncements [Axis]
Type of Adoption [Domain]
Type of Adoption [Domain]
Adjustments for Change in Accounting Principle [Axis]
Adjustments for Change in Accounting Principle [Axis]
Adjustments for Change in Accounting Principle [Domain]
Adjustments for Change in Accounting Principle [Domain]
Stockholders' Equity
Shares, Issued
Shares, Issued
Treasury Stock, Shares
Net income
Stockholders' Equity, Other Shares
Stockholders' Equity, Other Shares
Stock Issued During Period, Shares, New Issues
Stock Issued During Period, Shares, New Issues
Stock Issued During Period, Value, New Issues
Stock Issued During Period, Value, New Issues
Stock Issued During Period, Shares, Treasury Stock Reissued
Stock Issued During Period, Shares, Treasury Stock Reissued
Stock Granted, Value, Share-based Compensation, Net of Forfeitures
Stock Granted, Value, Share-based Compensation, Net of Forfeitures
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures
Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax
Stockholders' Equity
Shares, Issued
Treasury Stock, Shares
Debt [Text Block]
Debt Disclosure [Text Block]
Capitalized Exploratory Well Costs [Abstract]
Capitalized Exploratory Well Costs [Table]
Capitalized Exploratory Well Costs [Table]
Capitalized Exploratory Well Costs [Table]
Capitalized Exploratory Well Costs [Line Items]
Capitalized Exploratory Well Costs [Line Items]
[Line Items] for Capitalized Exploratory Well Costs [Table]
Capitalized Exploratory Well Costs [Text Block]
Capitalized Exploratory Well Costs [Text Block]
Capitalized Exploratory Well Costs [Text Block]
Acquisitions & Divestitures [Text Block]
Mergers, Acquisitions and Dispositions Disclosures [Text Block]
Basis of Presentation [Text Block]
Nature of Operations [Text Block]
Share-based Compensation Expense [Table Text Block]
Share-based Compensation Expense [Table Text Block]
[Table Text Block] for Share-based Compensation Expense [Table]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]
Schedule of Share-based Compensation, Restricted Share Awards Activity [Table Text Block]
Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]
Schedule of Other Share-based Compensation, Activity [Table Text Block]
Schedule of Other Share-based Compensation, Activity [Table Text Block]
Measurement Basis [Axis]
Measurement Basis [Axis]
Fair Value Measurement [Domain]
Fair Value Measurement [Domain]
Portion at Fair Value Measurement [Member]
Portion at Fair Value Measurement [Member]
Reported Value Measurement [Member]
Reported Value Measurement [Member]
Estimate of Fair Value Measurement [Member]
Estimate of Fair Value Measurement [Member]
Cash and Cash Equivalents, at Carrying Value
Long-term debt, fair value
Long-term Debt, Fair Value
Capitalized exploratory well costs, beginning balance
Capitalized Exploratory Well Costs
Additions to capitalized exploratory well costs pending the determination of proved reserves
Capitalized Exploratory Well Cost, Period Increase (Decrease)
Reclassification to proved properties after the determination of proved reserves
Reclassification to Well, Facilities, and Equipment Based on Determination of Proved Reserves
Capitalized exploratory well costs charged to expense
Capitalized Exploratory Well Cost, Charged to Expense
Capitalized exploratory well costs, ending balance
Commitments and Contingencies Disclosure [Abstract]
Loss Contingencies [Table]
Loss Contingencies [Table]
Litigation Case [Axis]
Litigation Case [Axis]
Litigation Case [Domain]
Litigation Case [Domain]
Rocky Mountain Resources Lawsuit [Member]
Rocky Mountain Resources Lawsuit [Member]
Rocky Mountain Resources Lawsuit [Member]
Gas Purchase Agreement Arbitration [Member]
Gas Purchase Agreement Arbitration [Member]
Gas Purchase Agreement Arbitration [Member]
Litigation Status [Axis]
Litigation Status [Axis]
Litigation Status [Domain]
Litigation Status [Domain]
Loss Contingency Nature [Axis]
Loss Contingency Nature [Axis]
Loss Contingency, Nature [Domain]
Loss Contingency, Nature [Domain]
Loss Contingencies [Line Items]
Loss Contingencies [Line Items]
Loss Contingency, Range of Possible Loss, Minimum
Loss on Contingency, Estimate of Possible Loss, Minimum
Loss on Contingency, Estimate of Possible Loss, Minimum
Loss Contingency, Range of Possible Loss, Maximum
Loss Contingency, Estimate of Possible Loss, Maximum
Loss Contingency, Estimate of Possible Loss, Maximum
Litigation Settlement, Amount
Litigation Settlement, Amount
Litigation Settlement Statutory Interest Rate
Litigation Settlement Statutory Interest Rate
Litigation Settlement Statutory Interest Rate
Loss Contingency Bond Posted
Loss Contingency Bond Posted
Loss Contingency Bond Posted
Employee Benefits [Text Block]
Pension and Other Postretirement Benefits Disclosure [Text Block]
Minimum [Member]
Minimum [Member]
Maximum [Member]
Maximum [Member]
Maximum Forecasted Production Covered By Derivatives
Maximum Forecasted Production Covered By Derivatives
Potential maximum amount of forecasted production covered by derivative contracts.
Expected Annual Production Covered By Derivatives
Expected Annual Production Covered By Derivatives
Expected Annual Production Covered By Derivatives
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value
Shares available for future grants
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant
Unrecognized compensation costs
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized
Weighted average period for recognition of equity-based compensation expense
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition
Award vesting period
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period
Total fair value of stock that vested during the period
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value
Capitalized Exploratory Well Costs [Table Text Block]
Capitalized Exploratory Well Costs [Table Text Block]
[Table Text Block] for Capitalized Exploratory Well Costs [Table]
Earnings Per Share [Text Block]
Earnings Per Share [Text Block]
Contingencies [Text Block]
Commitments and Contingencies Disclosure [Text Block]
Subsequent Event [Abstract]
Subsequent Event [Abstract]
Subsequent Event [Table]
Subsequent Event [Table]
Subsequent Event Type [Axis]
Subsequent Event Type [Axis]
Subsequent Event Type [Domain]
Subsequent Event Type [Domain]
Subsequent Event [Line Items]
Subsequent Event [Line Items]
Gas Swaps [Member]
Gas Swaps [Member]
Gas Swaps [Member]
Oil Swaps [Member]
Oil Swaps [Member]
Oil Swaps [Member]
Gas Collars [Member]
Gas Collars [Member]
Gas Collars [Member]
Gas Basis Swaps [Member]
Gas Basis Swaps [Member]
Gas Basis Swaps [Member]
Gas Purchase Swaps [Member]
Gas Purchase Swaps [Member]
Gas Purchase Swaps [Member]
Derivative Contract Year [Axis]
Derivative Contract Year [Axis]
Tabular presentation of derivative instruments by year of contract.
Derivative Contract Year [Domain]
Derivative Contract Year [Domain]
Tabular presentation of derivative instruments by year of contract.
Year 2016 [Member]
Year 2016 [Member]
Year 2016 [Member]
Year 2017 [Member]
Year 2017 [Member]
Year 2017 [Member]
Year 2018 [Member]
Year 2018 [Member]
Year 2018 [Member]
Energy Commodities Exchange [Axis]
Energy Commodities Exchange [Axis]
Exchange where various commodities and derivatives products are traded
Energy Commodities Exchange Abbreviation [Domain]
Energy Commodities Exchange Abbreviation [Domain]
Exchange abbreviation where various commodities and derivatives products are traded.
NYMEX HH [Member]
NYMEX HH [Member]
NYMEX HH [Member]
IFNPCR [Member]
IFNPCR [Member]
Energy Commodities Exchange Abbreviation
NYMEX WTI [Member]
NYMEX WTI [Member]
Energy Commodities Exchange Abbreviation
NYMEX HH LESS IFNPCR [Member]
NYMEX HH LESS IFNPCR [Member]
NYMEX HH LESS IFNPCR [Member]
Derivative Volumes
Derivative, Nonmonetary Notional Amount
Average Swap Price per Unit
Average Swap Price per Unit
Average Swap Price per Unit
Weighted-Average Differential
Underlying, Derivative
Derivative Average Price Floor
Derivative Average Price Floor
Derivative Average Price Floor
Derivative Average Price Ceiling
Derivative Average Price Ceiling
Derivative Average Price Ceiling
Revision of Financial Statements [Table]
Revision of Financial Statements [Table]
As reported [Member]
As reported [Member]
As reported [Member]
As revised [Member]
As revised [Member]
As revised [Member]
Change [Member]
Change [Member]
Change [Member]
Revision of Financial Statements [Line Items]
Revision of Financial Statements [Line Items]
[Line Items] for Revision of Financial Statements [Table]
Revenue from Purchased Oil and Gas
Revenue from Purchased Oil and Gas
Revenues
Revenues
Cost of Purchased Oil and Gas
Cost of Purchased Oil and Gas
Operating Expenses
Schedule of Net Benefit Costs [Table Text Block]
Schedule of Net Benefit Costs [Table Text Block]
Amortization of net actuarial loss, income tax expense
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax
Amortization of prior service cost, income tax expense
Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), Tax
Document And Entity Information [Abstract]
Document and Entity Information [Abstract]
Entity Registrant Name
Entity Registrant Name
Entity Central Index Key
Entity Central Index Key
Current Fiscal Year End Date
Current Fiscal Year End Date
Entity Well-known Seasoned Issuer
Entity Well-known Seasoned Issuer
Entity Voluntary Filers
Entity Voluntary Filers
Entity Current Reporting Status
Entity Current Reporting Status
Entity Filer Category
Entity Filer Category
Entity Common Stock, Shares Outstanding
Entity Common Stock, Shares Outstanding
Document Fiscal Year Focus
Document Fiscal Year Focus
Document Fiscal Period Focus
Document Fiscal Period Focus
Document Type
Document Type
Amendment Flag
Amendment Flag
Document Period End Date
Document Period End Date