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Contract Assets and Liabilities - Additional information (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Contract Assets and Liabilities        
Revenue recognized during period $ 11.9 $ 16.9 $ 39.4 $ 22.6