Summary of Property and Equipment (Detail) (USD $)	3 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Apr. 24, 2013
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets to be Disposed of	$ 117,900,000
Oil and gas properties:
Proved	440,606,000	460,255,000
Unproved	102,492,000	101,520,000
Total oil and gas properties	543,098,000	561,775,000
Capitalized Costs, Proved Properties	2,575,966,000	2,593,700,000	267,688,000
Support equipment	2,598,557,000	2,615,213,000
Total other property and equipment	3,141,655,000	3,176,988,000
Accumulated depreciation, depletion and amortization	(933,901,000)	(939,684,000)
Property and equipment, net (successful efforts method)	2,207,754,000	2,237,304,000
Support Equipment and Facilities [Member]
Oil and gas properties:
Support equipment	$ 22,591,000	$ 21,513,000