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Commitments and Contingencies - Additional Information (Detail)
$ in Millions
 1 Months Ended 9 Months Ended 12 Months Ended
Nov. 22, 2017
USD ($)
Dec. 31, 2017
USD ($)
T
Mar. 31, 2016
USD ($)
Jul. 31, 2017
USD ($)
Significant Purchase And Supply Commitment [Line Items]        
Cash compensation on termination of employment, maximum   $ 68.0    
Fast Crew Supply Boat [Member]        
Significant Purchase And Supply Commitment [Line Items]        
Number of vessels under construction   1    
Remaining accumulated cost reclassified from construction in progress to other assets as insurance receivable     $ 5.6  
Remaining insurance receivable   $ 1.8   $ 1.8
Vessel Commitments        
Significant Purchase And Supply Commitment [Line Items]        
Significant commitment, new construction deadweight tons capacity | T   5,400    
'Number of Vessels, commitments   2    
Settlement agreement, date November 22, 2017      
Delivery date of first PSV 2017-11      
Final installment paid $ 4.3      
Delivery date of second PSV 2018-07      
Remaining installment payment for second PSV $ 4.5      
Settlement credit for future dry docking services $ 0.3      
'Vessel under construction, fair value, after fresh start accounting       $ 7.0