Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	6 Months Ended
	Nov. 30, 2010	Jun. 30, 2017	Dec. 31, 2016
Long-term Purchase Commitment [Line Items]
Total future drilling commitments at balance sheet date		$ 144.0
Drilling commitments due remainder of current year		55.0
Drilling commitments Year Two		59.0
Drilling Commitments Year Three		29.0
Drilling Commitments Year Four		$ 1.0
Pipeline commitments, end date		2028
Future Drilling Commitments End Date		2020-02
Purchase Obligation, total		$ 1,200.0
Purchase Obligation, due in remainder of current year		115.0
Purchase Obligation, due second year		245.0
Purchase Obligation, due third year		233.0
Purchase Obligation, due fourth year		101.0
Purchase Obligation, due fifth year		89.0
Purchase Obligation, due after fifth year		424.0
Damages sought in litigation matter	$ 200.0
Legal proceedings recorded as a liability under other noncurrent liabilities		$ (6.5)	$ (6.5)