Gross Carrying Amount and Accumulated Amortization of Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 48,000	$ 25,500
Accumulated Amortization	(32,427)	(22,768)
Net Carrying Amount	15,573	2,732
Customer Relationships
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	25,500	25,500
Accumulated Amortization	(24,589)	(22,768)
Net Carrying Amount	911	$ 2,732
Favorable Drilling Contracts
Acquired Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	22,500
Accumulated Amortization	(7,838)
Net Carrying Amount	$ 14,662