Net Property and Equipment - Schedule of Net Property and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment, Net [Abstract]
Proved crude oil and natural gas properties	$ 17,045,967	$ 12,423,878
Unproved crude oil and natural gas properties	966,080	1,181,268
Service properties, equipment and other	274,584us-gaap_PropertyPlantAndEquipmentOther	236,233us-gaap_PropertyPlantAndEquipmentOther
Total property and equipment	18,286,631us-gaap_PropertyPlantAndEquipmentGross	13,841,379us-gaap_PropertyPlantAndEquipmentGross
Accumulated depreciation, depletion and amortization	(4,650,779)	(3,120,107)
Net property and equipment	$ 13,635,852us-gaap_PropertyPlantAndEquipmentNet	$ 10,721,272us-gaap_PropertyPlantAndEquipmentNet

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Amount before accumulated depreciation, depletion and amortization of other physical assets used in the normal conduct of business to produce goods and services and not intended for resale.

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Oil and Gas properties with proved reserves under the successful effort method.

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Oil and Gas properties with unproved reserves under the successful effort method.

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