Condensed Consolidating Financial Information - Schedule of Condensed Consolidating Statement of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net cash provided by operating activities	$ 88,361	$ 208,267
Cash flows from investing activities:
Capital expenditures	(359,113)	(280,895)
Proceeds from sale of properties	0	321,943
Derivative settlements	109,259	(2,239)
Other investing activities	(828)	(6,147)
Net cash provided by (used in) investing activities	(250,682)	34,901
Cash flows from financing activities:
Proceeds from sale of common stock	463,218	0
Proceeds from revolving credit facility	145,000	0
Principal payments on revolving credit facility	(480,000)	(275,570)
Other financing activities	(1,520)	(3,201)
Net cash provided by (used in) financing activities	126,698	(278,771)
Decrease in cash and cash equivalents	(35,623)	(35,603)
Beginning of period	45,811	91,901
End of period	10,188	56,298
Parent/Issuer [Member]
Cash flows from operating activities:
Net cash provided by operating activities	(7,988)	(56,630)
Cash flows from investing activities:
Net cash provided by (used in) investing activities	0
Cash flows from financing activities:
Proceeds from sale of common stock	463,218
Other financing activities	(455,232)	23,289
Net cash provided by (used in) financing activities	7,986	23,289
Decrease in cash and cash equivalents	(2)	(33,341)
Beginning of period	776	34,277
End of period	774	936
Combined Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net cash provided by operating activities	96,349	264,897
Cash flows from investing activities:
Capital expenditures	(359,113)	(280,895)
Proceeds from sale of properties		321,943
Derivative settlements	109,259
Other investing activities	(828)	(6,147)
Net cash provided by (used in) investing activities	(250,682)	34,901
Cash flows from financing activities:
Proceeds from revolving credit facility	145,000
Principal payments on revolving credit facility	(480,000)	(275,570)
Other financing activities	453,712	(26,490)
Net cash provided by (used in) financing activities	118,712	(302,060)
Decrease in cash and cash equivalents	(35,621)	(2,262)
Beginning of period	45,035	57,624
End of period	$ 9,414	$ 55,362

Proceeds from (Payments for) Other Financing Activities, Condensed Consolidating

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

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The cash outflow for exploration and development of oil and gas properties. It includes cash payments related to development of oil and gas wells drilled at previously untested geologic structures (to determine the presence of oil or gas) and wells drilled at sites where the presence of oil or gas has already been established (to extract the oil or gas).

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