Revenue, Contract Assets and Liabilities and Other Contract Matters -Summary of Remaining Performance Obligation by Operating Segment (Parenthetical) (Details) $ in Millions	Sep. 30, 2020 USD ($) vessel	Mar. 31, 2018 vessel
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Number of multi-purpose service vessels | vessel	2	2
Shipyard | Disputes
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation | $	$ 21.9