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Gross Carrying Amount and Accumulated Amortization of Intangible Assets (Detail) - USD ($)
$ in Thousands
Sep. 30, 2017
Dec. 31, 2016
Acquired Finite Lived Intangible Assets [Line Items]    
Gross Carrying Amount $ 48,000 $ 25,500
Accumulated Amortization (39,018) (22,768)
Net Carrying Amount 8,982 2,732
Customer Relationships    
Acquired Finite Lived Intangible Assets [Line Items]    
Gross Carrying Amount 25,500 25,500
Accumulated Amortization (25,500) (22,768)
Net Carrying Amount   $ 2,732
Favorable Drilling Contracts    
Acquired Finite Lived Intangible Assets [Line Items]    
Gross Carrying Amount 22,500  
Accumulated Amortization (13,518)  
Net Carrying Amount $ 8,982