Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	6 Months Ended
	Nov. 30, 2010	Jun. 30, 2016	Dec. 31, 2015
Long-term Purchase Commitment [Line Items]
Total future drilling commitments at balance sheet date		$ 319.0
Drilling commitments due remainder of current year		97.0
Drilling commitments Year Two		136.0
Drilling Commitments Year Three		62.0
Drilling Commitments Year Four		$ 24.0
Future Drilling Commitments End Date		2019-12
Damages sought in litigation matter	$ 200.0
Legal proceedings recorded as a liability under other noncurrent liabilities		$ (6.1)	$ (6.1)
Pipeline Transportation of Crude Oil and Natural Gas [Member]
Long-term Purchase Commitment [Line Items]
Pipeline commitments, end date		2027
Purchase Obligation, total		$ 893.0
Purchase Obligation, due in remainder of current year		107.0
Purchase Obligation, due second year		207.0
Purchase Obligation, due third year		208.0
Purchase Obligation, due fourth year		154.0
Purchase Obligation, due fifth year		47.0
Purchase Obligation, Due after Fifth Year		$ 170.0