Annual report pursuant to Section 13 and 15(d)

Schedule II - Valuation and Qualifying Accounts (Detail)

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Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Allowance for bad debt      
Movement in Valuation Allowances and Reserves [Roll Forward]      
Balance at beginning of year $ 8,259 $ 8,694 $ 11,188
Charged to cost and expenses 444 1,483 341
Charged to other accounts (414) 4 (825)
Deductions (725) (1,922) (2,010)
Balance at end of year 7,564 8,259 8,694
Allowance for obsolete rig materials and supplies      
Movement in Valuation Allowances and Reserves [Roll Forward]      
Balance at beginning of year 1,166 626 530
Charged to cost and expenses 65 978 0
Charged to other accounts 0 (3) 236
Deductions (422) (435) (140)
Balance at end of year 809 1,166 626
Deferred tax valuation allowance      
Movement in Valuation Allowances and Reserves [Roll Forward]      
Balance at beginning of year 171,133 51,105 9,922
Charged to cost and expenses (14,625) 117,707 40,676
Charged to other accounts 1,406 2,321 507
Deductions 0 0 0
Balance at end of year $ 157,914 $ 171,133 $ 51,105