Annual report pursuant to Section 13 and 15(d)

Revenue, Contract Assets and Liabilities and Other Contract Matters - Summary of Contract with Customer, Asset and Liability (Parenthetical) (Details)

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Revenue, Contract Assets and Liabilities and Other Contract Matters - Summary of Contract with Customer, Asset and Liability (Parenthetical) (Details)
$ in Millions
12 Months Ended
Dec. 31, 2019
USD ($)
vessel
Dec. 31, 2018
USD ($)
Mar. 31, 2018
vessel
Revenue From Contract With Customer [Abstract]      
Number of multi-purpose service vessels | vessel 2   2
Contract with customer, liability, revenue recognized $ 14.3 $ 5.1  
Contract with customer, liability, accrued contract losses, current $ 6.4 $ 2.4