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Summary of Pro Forma Impact of Merger (Detail) - GulfMark - USD ($)
$ / shares in Units, $ in Millions
5 Months Ended 12 Months Ended
Dec. 31, 2017
Dec. 31, 2018
Business Acquisition [Line Items]    
Revenues $ 223,254 $ 500,118
Net loss $ (13,088) $ (196,057)
Basic loss per common share $ (0.44) $ (5.66)
Diluted loss per common share $ (0.44) $ (5.66)