Divestitures - Additional Information (Detail) (USD $)	6 Months Ended	0 Months Ended	1 Months Ended
	Jun. 30, 2014	Jan. 16, 2014 Cut Off and Clovelly Fields [Member]	Jan. 31, 2014 Hatch Point Field [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of interest cash consideration	$ 51,955,000	$ 44,800,000	$ 9,700,000
Estimates asset retirement obligations		9,200,000	1,200,000
Gain or loss recognized from the sale of interest			$ 0