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Goodwill by Operating Segment (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Goodwill [Line Items]      
Balance at beginning of period $ 395,060,000 $ 410,756,000  
Measurement period adjustment   2,104,000  
Impairment (395,060,000) (17,800,000) $ (211,129,000)
Balance at end of period   395,060,000 410,756,000
Contract Drilling      
Goodwill [Line Items]      
Balance at beginning of period 395,060,000 395,060,000  
Impairment $ (395,060,000) 0 0
Balance at end of period   395,060,000 395,060,000
Other Operations      
Goodwill [Line Items]      
Balance at beginning of period   15,696,000  
Measurement period adjustment   2,104,000  
Impairment   $ (17,800,000)  
Balance at end of period     $ 15,696,000