Summary of Significant Accounting Policies - Summary of Carrying Amounts and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Derivative Financial Instruments	$ 62,277	$ 15,401
Bank Credit Facility
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt, Carrying Value	(1,265,000)	(450,000)
Long-term debt, Fair Value	(1,265,000)	(450,000)
Level 2 \| 7.50% Senior Notes due 2025 \| Long Term Debt
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt, Carrying Value	(450,703)
Long-term debt, Fair Value	(503,125)
Level 2 \| 9.75% Senior Notes due 2026 \| Long Term Debt
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt, Carrying Value	(819,277)	(817,066)
Long-term debt, Fair Value	(709,750)	(720,375)
Commodity Swaps, Options and Basis Swaps \| Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Derivative Financial Instruments	84,260	15,401
Derivative financial asset, Fair value	$ 84,260	$ 15,401

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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