Summary of Significant Accounting Policies - Schedule of Contract Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Contract assets	$ 294.3	$ 243.5
Reserve for overhead rate disallowance	(5.7)	(19.4)
Contract assets, net of reserve	288.6	224.1
Contract liabilities	407.2	262.3
Net contract liabilities, net of reserve	$ (118.6)	$ (38.2)