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Accounts Receivable, net (Details) - USD ($)
$ in Millions
Mar. 31, 2021
Dec. 31, 2020
Receivables [Abstract]    
Contracts in progress $ 114.6 $ 118.6
Unbilled retentions 50.9 50.3
Trade receivables 7.2 7.5
Other receivables 14.3 8.9
Allowance for doubtful accounts (0.6) (0.6)
Total $ 186.4 $ 184.7