Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Nov. 30, 2010	Sep. 30, 2016	Dec. 31, 2015
Long-term Purchase Commitment [Line Items]
Total future drilling commitments at balance sheet date		$ 250.0
Drilling commitments due remainder of current year		49.0
Drilling commitments Year Two		134.0
Drilling Commitments Year Three		44.0
Drilling Commitments Year Four		21.0
Drilling Commitments Year Five		$ 2.0
Future Drilling Commitments End Date		2020-02
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		$ 849.0
Purchase Obligation, due in remainder of current year		55.0
Purchase Obligation, due second year		215.0
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