Fair Value Disclosures [Abstract]
Fair Value Measurements, Recurring and Nonrecurring [Table]
Fair Value Measurements, Recurring and Nonrecurring [Table]
Measurement Frequency [Axis]
Measurement Frequency [Axis]
Fair Value, Measurement Frequency [Domain]
Fair Value, Measurement Frequency [Domain]
Fair Value, Hierarchy [Axis]
Fair Value, Hierarchy [Axis]
Fair Value Hierarchy [Domain]
Fair Value Hierarchy [Domain]
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]
Business Combinations [Abstract]
Acquisitions & Divestitures [Text Block]
Mergers, Acquisitions and Dispositions Disclosures [Text Block]
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table]
Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table]
Operating Activities [Axis]
Operating Activities [Axis]
Operating Activities [Domain]
Operating Activities [Domain]
Award Type [Axis]
Award Type [Axis]
Equity Award [Domain]
Equity Award [Domain]
Stock Options [Member]
Employee Stock Option [Member]
Restricted Share Awards [Member]
Restricted Stock [Member]
Performance Share Units [Member]
Performance Share Units [Member]
Incremental common shares attributable to performance share units.
Restricted Share Units (RSUs) [Member]
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grants
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant
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
Unrecognized compensation costs
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized
Weighted average vesting period
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
Business Acquisition, Pro Forma Information [Table Text Block]
Business Acquisition, Pro Forma Information [Table Text Block]
Share-based Compensation Expense [Table]
Share-based Compensation Expense [Table]
Share-based Compensation Expense [Table]
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
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]
Subsequent Events [Text Block]
Subsequent Events [Text Block]
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation [Text Block]
Nature of Operations [Text Block]
Statement of Financial Position [Abstract]
LIABILITIES AND EQUITY
Liabilities and Equity [Abstract]
EQUITY
Stockholders' Equity Attributable to Parent [Abstract]
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
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 and SERP [Member]
Pension Plan and SERP [Member]
Pension Plan and SERP [Member]
Medical Plan [Member]
Medical Plan [Member]
Medical 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, Curtailments
Periodic expense
Defined Benefit Plan, Net Periodic Benefit Cost
Business Combination, Separately Recognized Transactions [Table]
Business Combination, Separately Recognized Transactions [Table]
Petroleum Reserves [Axis]
Petroleum Reserves [Axis]
Type of Reserve [Domain]
Type of Reserve [Domain]
Proved Property [Member]
Proved Property [Member]
Proved Property [Member]
Unproved Property [Member]
Unproved Property [Member]
Unproved Property [Member]
Asset Retirement Obligation Costs [Member]
Asset Retirement Obligation Costs [Member]
Bargain Purchase Gain [Member]
Bargain Purchase Gain [Member]
Bargain Purchase Gain [Member]
Business Acquisition [Axis]
Business Acquisition [Axis]
Business Acquisition, Acquiree [Domain]
Business Acquisition, Acquiree [Domain]
2016 Permian Basin Acquisition [Member]
2016 Permian Basin Acquisition [Member]
2016 Permian Basin Acquisition [Member]
Business Combination, Separately Recognized Transactions [Axis]
Business Combination, Separately Recognized Transactions [Axis]
Business Combination, Separately Recognized Transactions [Domain]
Business Combination, Separately Recognized Transactions [Domain]
Income Statement Location [Axis]
Income Statement Location [Axis]
Income Statement Location [Domain]
Income Statement Location [Domain]
Balance Sheet Location [Axis]
Balance Sheet Location [Axis]
Balance Sheet Location [Domain]
Balance Sheet Location [Domain]
Business Combination, Separately Recognized Transactions [Line Items]
Business Combination, Separately Recognized Transactions [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net
Earnings Per Share [Abstract]
Components of basic and diluted shares used in EPS [Table Text Block]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]
Restructuring and Related Activities [Abstract]
Schedule of Restructuring and Related Costs [Table]
Schedule of Restructuring and Related Costs [Table]
Segments [Axis]
Segments [Axis]
Segments [Domain]
Segments [Domain]
Restructuring Type [Axis]
Restructuring Type [Axis]
Type of Restructuring [Domain]
Type of Restructuring [Domain]
Restructuring Cost and Reserve [Line Items]
Restructuring Cost and Reserve [Line Items]
Schedule of Restricted Share Unit Transactions [Abstract]
Schedule of Restricted Share Unit Transactions [Abstract]
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
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, 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
Asset Retirement Obligation [Abstract]
Asset retirement obligations rollforward [Table Text Block]
Schedule of Change in Asset Retirement Obligation [Table Text Block]
Schedule of Net Benefit Costs [Table Text Block]
Schedule of Net Benefit Costs [Table Text Block]
Statement of Comprehensive Income [Abstract]
Net income (loss)
Net Income (Loss) Attributable to Parent
Postretirement medical plan change
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax
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 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
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
Other comprehensive income
Other Comprehensive Income (Loss), Net of Tax
Comprehensive income (loss)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent
Postretirement medical plan changes, income tax expense
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, 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
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
Employee Benefits [Text Block]
Pension and Other Postretirement Benefits Disclosure [Text Block]
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
Plan Name [Axis]
Plan Name [Axis]
Plan Name [Domain]
Plan Name [Domain]
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 forfeited
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Number of Shares
Options canceled
Share-based Compensation Arrangement by Share-based Payment Award, Options, Other Increases (Decreases) in Period
Outstanding at end of period
Options exercisable, shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number
Unvested options, shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares
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, forfeited in period
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations 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, weighted average exercise price
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price
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.
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]
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]
Capitalized Exploratory Well Costs [Abstract]
Capitalized Exploratory Well Costs [Table]
Capitalized Exploratory Well Costs [Table]
Capitalized Exploratory Well Costs [Table]
Property, Plant and Equipment, Type [Axis]
Property, Plant and Equipment, Type [Axis]
Property, Plant and Equipment, Type [Domain]
Property, Plant and Equipment, Type [Domain]
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]
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]
Capitalized Exploratory Well Costs [Table Text Block]
Capitalized Exploratory Well Costs [Table Text Block]
[Table Text Block] for Capitalized Exploratory Well Costs [Table]
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]
6.80% 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, Gross
Long-term Debt, Gross
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
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
Other Divestitures [Abstract]
Other Divestitures [Abstract]
Divestitures [Table]
Divestitures [Table]
Divestitures [Table]
Business Divestiture [Axis]
Business Divestiture [Axis]
Business Divestiture [Axis]
Business Divestiture [Domain]
Business Divestiture [Domain]
[Domain] for Business Divestiture [Axis]
Non-core properties Divestitures [Member]
Non-core properties Divestitures [Member]
Non-core properties Divestitures [Member]
Divestitures [Line Items]
Divestitures [Line Items]
[Line Items] for Divestitures [Table]
Proceeds from Sale of Oil and Gas Property and Equipment
Proceeds from Sale of Oil and Gas Property and Equipment
Net gain (loss) from asset sales
Gain (Loss) on Disposition of Property Plant Equipment
Payments to acquire oil and gas property
Payments to Acquire Oil and Gas Property
Statement [Table]
Statement [Table]
Scenario [Axis]
Scenario [Axis]
Scenario, Unspecified [Domain]
Scenario, Unspecified [Domain]
Statement [Line Items]
Statement [Line Items]
Project [Axis]
Project [Axis]
Project [Domain]
Project [Domain]
Central Basin Platform [Member]
Central Basin Platform [Member]
Central Basin Platform [Member]
Capitalized exploratory well costs, beginning balance
Capitalized Exploratory Well Costs
Additions to capitalized exploratory well costs
Capitalized Exploratory Well Cost, Period Increase (Decrease)
Reclassifications to proved properties
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
Share-Based Compensation [Text Block]
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]
Income Statement [Abstract]
REVENUES
Revenues [Abstract]
Oil sales
Oil and Condensate Revenue
Gas sales
Natural Gas Production Revenue
NGL sales
Natural Gas Midstream Revenue
Other revenue
Gas Gathering, Transportation, Marketing and Processing Revenue
Purchased oil and gas sales
Revenue from Purchased Oil and Gas
Total Revenues
Oil and Gas Revenue
OPERATING EXPENSES
Operating Expenses [Abstract]
Purchased oil and gas expense
Refining and Marketing Costs
Lease operating expense
Oil and Gas Property, Lease Operating Expense
Transportation and processing 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
OPERATING INCOME (LOSS)
Operating Income (Loss)
Realized and unrealized gains (losses) on derivative contracts (Note 7)
Gain (Loss) on Derivative Instruments, Net, 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
Asset Retirement Obligations [Text Block]
Asset Retirement Obligation Disclosure [Text Block]
Schedule of Impaired Long-Lived Assets Held and Used [Table]
Schedule of Impaired Long-Lived Assets Held and Used [Table]
Williston & Permian Basins [Member]
Williston & Permian Basins [Member]
Williston & Permian Basins [Member]
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]
Oil and Gas Production Type [Axis]
Production Type [Domain]
Production Type [Domain]
Impaired Long-Lived Assets Held and Used [Line Items]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment
Impairment of Oil and Gas Properties
Goodwill impairment
Goodwill, Acquired During Period
Schedule of Business Acquisitions, by Acquisition [Table]
Schedule of Business Acquisitions, by Acquisition [Table]
Class of Stock [Axis]
Class of Stock [Axis]
Class of Stock [Domain]
Class of Stock [Domain]
Business Acquisition [Line Items]
Business Acquisition [Line Items]
Payments for acquisitions
Payments to Acquire Businesses, Gross
Net acres
Gas and Oil Area, Developed, Net
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual
Bargain purchase gain from acquisition
Business Combination, Bargain Purchase, Gain Recognized, Amount
Fair Value, by Balance Sheet Grouping [Table]
Fair Value, by Balance Sheet Grouping [Table]
Measurement Basis [Axis]
Measurement Basis [Axis]
Fair Value Measurement [Domain]
Fair Value Measurement [Domain]
Reported Value Measurement [Member]
Reported Value Measurement [Member]
Estimate of Fair Value Measurement [Member]
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Fair Value, Gross Asset
Derivative Asset, Fair Value, Gross Asset
Cash and Cash Equivalents, at Carrying Value
Cash and Cash Equivalents, at Carrying Value
Checks outstanding in excess of cash balances
Bank Overdrafts
Long-term debt
Long-term Debt
Long-term debt, fair value
Long-term Debt, Fair Value
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]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustments [Table]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustments [Table]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenues
Pro Forma Revenue
Business Acquisition, Pro Forma Revenue
Pro Forma Net Income (Loss)
Business Acquisition, Pro Forma Net Income (Loss)
Pro Forma Earnings Per Share, Basic
Business Acquisition, Pro Forma Earnings Per Share, Basic
Pro Forma Earnings Per Share, Diluted
Business Acquisition, Pro Forma Earnings Per Share, Diluted
Pinedale Divestiture [Abstract]
Pinedale Divestiture [Abstract]
Oil and Gas Production Type [Axis]
One-time Termination Benefits [Member]
One-time Termination Benefits [Member]
Employee Relocation [Member]
Employee Relocation [Member]
Pinedale Divestiture [Member]
Pinedale Divestiture [Member]
Pinedale Divestiture [Member]
Oil and Gas Delivery Commitments and Contracts [Axis]
Oil and Gas Delivery Commitments and Contracts [Axis]
Oil and Gas Delivery Commitments and Contracts
Oil and Gas Delivery Commitments and Contracts, Oil Producing Property [Domain]
Total [Member]
Total [Member]
Total [Member]
Short-term [Member]
Short term [Member]
Derivative contracts with maturities of one year or less.
Long-term [Member]
Long term [Member]
Derivative contracts with maturities in excess of one year.
Minimum volume commitment
Long-term Purchase Commitment, Amount
Minimum volume commitment remaining
Purchase Commitment, Remaining Minimum Amount Committed
INCOME (LOSS) BEFORE INCOME TAXES
Restructuring costs, expected cost
Restructuring and Related Cost, Expected Cost
Restructuring costs, cost incurred to date
Restructuring and Related Cost, Cost Incurred to Date
Debt Outstanding [Table Text Block]
Schedule of Debt [Table Text Block]
Other Acquisitions [Abstract]
Other Acquisitions [Abstract]
Noncash or Part Noncash Acquisitions by Unique Description [Axis]
Noncash or Part Noncash Acquisitions by Unique Description [Axis]
Noncash or Part Noncash Acquisition, Name [Domain]
Noncash or Part Noncash Acquisition, Name [Domain]
Cash [Member]
Cash [Member]
Accounts Receivable [Member]
Accounts Receivable [Member]
Other Acquisitions [Member]
Other Acquisitions [Member]
Other Acquisitions [Member]
Bargain purchase gain from acquisition
Acquisition Costs, Period Cost
Acquisition Costs, Period Cost
Goodwill
Derivative [Table]
Derivative [Table]
Fair Value, Inputs, Level 2 [Member]
Fair Value, Inputs, Level 2 [Member]
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 Liability, Fair Value, Gross
Derivative Liability, Fair Value, Gross Liability
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
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]
5.375% 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]
Less unamortized discount
Debt Instrument, Unamortized Discount
Total long-term debt outstanding
Long-term Debt, Excluding Current Maturities
Less: current portion of long-term debt
Long-term Debt, Current Maturities
Fair Value, Measurements, Fair Value Hierarchy [Domain]
Level 1 [Member]
Fair Value, Inputs, Level 1 [Member]
Level 2 [Member]
Level 3 [Member]
Fair Value, Inputs, Level 3 [Member]
Financial Assets
Derivative Asset [Abstract]
Derivative Asset, Fair Value, Gross
Derivative Asset
Derivative Asset
Net amount of derivative assets presented on condensed consolidated balance sheets
Derivative Asset, Fair Value, Amount Offset Against Collateral
Derivative Liability
Derivative Liability
Financial liabilities
Derivative Liability [Abstract]
Income Tax Disclosure [Abstract]
Effective income tax rate
Effective Income Tax Rate Reconciliation, Percent
Derivative Instruments and Hedging Activities Disclosure [Text Block]
Derivative Instruments and Hedging Activities Disclosure [Text Block]
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
Earnings Per Share [Text Block]
Earnings Per Share [Text Block]
Statement of Cash Flows [Abstract]
OPERATING ACTIVITIES
Net Cash Provided by (Used in) Operating Activities [Abstract]
Adjustments to reconcile net income (loss) to net cash provided by (used in) 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)
Bargain purchase gain from acquisition
Other non-cash activity
Other Operating Activities, Cash Flow Statement
Dry hole exploratory well expense
Share-based compensation
Share-based Compensation
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
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
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
Repayments of senior notes
Repayments of Long-term Debt
Long-term debt issuance costs paid
Payments of Debt Issuance Costs
Proceeds from credit facility
Proceeds from Long-term Lines of Credit
Repayments of credit facility
Repayments of Long-term Lines of Credit
Treasury stock repurchases
Payments for Repurchase of 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
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 (refund received) 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
Change in capital expenditure accruals and other non-cash adjustments
Change in capital expenditure accruals and other non-cash adjustments
Debt [Text Block]
Debt Disclosure [Text Block]
2017 Permian Basin Acquisition [Member]
2017 Permian Basin Acquisition [Member]
2017 Permian Basin Acquisition [Member]
Permian Basin Acquisition [Member]
Permian Basin Acquisition [Member]
Permian Basin Acquisition [Member]
Additional acquisitions in the Permian Basin [Member]
Additional acquisitions in the Permian Basin [Member]
Additional acquisitions in the Permian Basin [Member]
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
Revisions
Asset Retirement Obligation, Revision of Estimate
Liabilities related to assets sold
Asset Retirement Obligations, Liabilities Related to Divestitures
Asset Retirement Obligations, Liabilities Related to Divestitures
Liabilities settled
Asset Retirement Obligation, Liabilities Settled
ARO liability, Ending Balance
Fair Value Measurements [Text Block]
Fair Value Disclosures [Text Block]
Pension Plan [Member]
Pension Plan [Member]
SERP [Member]
SERP [Member]
SERP [Member]
Contributions by Employer
Defined Benefit Plan, Contributions by Employer
Estimated Future Employer Contributions in Current Fiscal Year
Defined Benefit Plans, Estimated Future Employer Contributions in Current Fiscal Year
Commitments and Contingencies Disclosure [Abstract]
Commitment and Contingencies [Text Block]
Commitments and Contingencies 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 Basis Swaps [Member]
Oil Basis Swaps [Member]
Oil Basis Swaps [Member]
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]
Production [Member]
Production [Member]
Production [Member]
Storage [Member]
Storage [Member]
Storage [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 2017 [Member]
Year 2017 [Member]
Year 2017 [Member]
Year 2018 [Member]
Year 2018 [Member]
Year 2018 [Member]
Year 2018 (July through December) [Member]
Year 2016 (July through December) [Member]
Year 2016 (July through December) [Member]
Year 2019 [Member]
Year 2019 [Member]
Year 2019 [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 WTI less Argus WTI Midland [Member]
NYMEX WTI less Argus WTI Midland [Member]
NYMEX WTI less Argus WTI Midland [Member]
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
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 Asset, Current
Hydrocarbon 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
Gathering 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
Gathering 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
Current Liabilities
Liabilities, Current [Abstract]
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
Current portion of long-term debt
Total Current Liabilities
Liabilities, Current
Long-term debt
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 9)
Commitments and Contingencies
Common stock – par value $0.01 per share; 500.0 million shares authorized; 242.2 million and 240.7 million shares issued, respectively
Common Stock, Value, Issued
Treasury stock – 1.7 million and 1.1 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]
NGL derivative contracts [Member]
NGL derivative contracts [Member]
NGL derivative contract [Member]
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.
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
Range [Axis]
Range [Axis]
Range [Domain]
Range [Domain]
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