Supplemental Information on Oil and Gas Producing Activities (Unaudited) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Capitalized Costs Relating to Oil and Gas Producing Activities
Proved properties	$ 6,515,221	$ 3,621,672
Unproved properties	2,060,936	1,513,136
Total	8,576,157	5,134,808
Accumulated depreciation and depletion	(802,665)	(383,921)
Net capitalized costs	7,773,492	4,750,887
Costs Incurred in Certain Oil and Gas Activities
Proved property	64,066	15,300	10,254
Unproved property	777,422	440,825	687,403
Development costs	1,536,193us-gaap_CostsIncurredDevelopmentCosts	780,583us-gaap_CostsIncurredDevelopmentCosts	678,276us-gaap_CostsIncurredDevelopmentCosts
Exploration costs	940,957us-gaap_CostsIncurredExplorationCosts	835,382us-gaap_CostsIncurredExplorationCosts	158,074us-gaap_CostsIncurredExplorationCosts
Total costs incurred	3,318,638	2,072,090	1,534,007
Results of Operations for Oil and Gas Producing Activities
Revenues	1,736,752	821,445	390,378
Operating expenses:
Production expenses	578,672	278,348	185,505
Exploration expenses	27,893	22,272	15,339
Depreciation and depletion	418,744	219,830	181,664
Impairment of unproved properties	15,198	10,928	13,032
Results of operations before income tax expense (benefit)	696,245	290,067	(5,162)
Income tax (expense) benefit	(263,126)	(110,805)	2,008
Results of operations	$ 433,119	$ 179,262	$ (3,154)

Amount of accumulated depreciation, depletion, amortization and valuation allowance relating to oil and gas producing activities.

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The sum of capitalized costs relating to oil and gas producing activities before accounting for accumulated depreciation.

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Capitalized costs of proved properties incurred for any combination mineral interests acquisitions; wells and related equipment; support equipment and facilities; and uncompleted wells and equipment and other costs not previously disclosed within this table.

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Capitalized costs of unproved properties incurred for any combination mineral interests acquisitions and other costs not previously disclosed within this table.

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Cost incurred, including capitalized costs and costs charged to expense, in acquisition of oil and gas properties.

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Costs incurred, including capitalized costs and costs charged to expense, associated with the acquisition of oil and gas properties that have proved reserves.

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Costs incurred, including capitalized costs and costs charged to expense, associated with the acquisition of oil and gas properties that have unproved reserves.

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Development costs incurred, including capitalized costs and costs charged to expense, in oil and gas activities.

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Exploration costs incurred, including capitalized costs and costs charged to expense, in oil and gas activities.

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Depreciation, depletion and amortization, and valuation provisions (impairments) related to oil and gas producing activities.

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Exploration costs from oil and gas producing activities.

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Costs related to the impairment of oil and gas properties.

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Income before income taxes for oil and gas producing activities.

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The results of operations for oil and gas producing activities, excluding corporate overhead and interest costs.

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Production (lifting) costs from oil and gas producing activities, including but not limited to lease operating expense, production and ad valorem taxes, and transportation expense.

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Total revenues from oil and gas producing activities.

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