Business Segment Information - Summarized Financial Information of Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Total revenues	$ 180,387us-gaap_OilAndGasRevenue	$ 349,519us-gaap_OilAndGasRevenue
Operating income (loss)	(33,635)us-gaap_OperatingIncomeLoss	329,080us-gaap_OperatingIncomeLoss
Other income (expense)	8,218us-gaap_NonoperatingIncomeExpense	(57,608)us-gaap_NonoperatingIncomeExpense
Income (loss) before income taxes	(25,417)	271,472
Property, Plant and Equipment, Net	5,329,362us-gaap_PropertyPlantAndEquipmentNet		5,186,786us-gaap_PropertyPlantAndEquipmentNet
Total assets	5,916,937us-gaap_Assets		5,938,412us-gaap_Assets
Exploration and Production [Member]
Segment Reporting Information [Line Items]
Total revenues	173,859	331,847
Well Services [Member]
Segment Reporting Information [Line Items]
Total revenues	50,905	52,406
Midstream Services [Member]
Segment Reporting Information [Line Items]
Total revenues	17,642	9,353
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	180,387	349,519
Operating income (loss)	(33,635)	329,080
Other income (expense)	8,218	(57,608)
Income (loss) before income taxes	(25,417)	271,472
Property, Plant and Equipment, Net	5,329,362		5,186,786
Total assets	5,916,937		5,938,412
Operating Segments [Member] \| Exploration and Production [Member]
Segment Reporting Information [Line Items]
Total revenues	173,859	331,847
Operating income (loss)	(42,247)	322,945
Other income (expense)	8,239	(57,660)
Income (loss) before income taxes	(34,008)	265,285
Property, Plant and Equipment, Net	5,194,649		5,074,588
Total assets	5,758,513		5,802,295
Operating Segments [Member] \| Well Services [Member]
Segment Reporting Information [Line Items]
Total revenues	2,708	15,827
Operating income (loss)	9,610	13,452
Other income (expense)	(2)	52
Income (loss) before income taxes	9,608	13,504
Property, Plant and Equipment, Net	56,270		58,767
Total assets	330,239		281,844
Operating Segments [Member] \| Midstream Services [Member]
Segment Reporting Information [Line Items]
Total revenues	3,820	1,845
Operating income (loss)	9,308	4,632
Other income (expense)	(19)
Income (loss) before income taxes	9,289	4,632
Property, Plant and Equipment, Net	207,713		172,394
Total assets	265,627		212,685
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	(62,019)	(44,087)
Operating income (loss)	(10,306)	(11,949)
Income (loss) before income taxes	(10,306)	(11,949)
Property, Plant and Equipment, Net	(129,270)		(118,963)
Total assets	(437,442)		(358,412)
Segment Reconciling Items [Member] \| Well Services [Member]
Segment Reporting Information [Line Items]
Total revenues	48,197	36,579
Segment Reconciling Items [Member] \| Midstream Services [Member]
Segment Reporting Information [Line Items]
Total revenues	$ 13,822	$ 7,508

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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The aggregate amount of income or expense from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business).

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Aggregate revenue during the period related to oil and gas business activities.

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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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