Supplementary Financial Information - Contract in Progress (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Offsetting [Abstract]
Costs incurred on contracts in progress	$ 1,611.6	$ 752.9
Estimated earnings	254.0	139.0
Cost earned on uncompleted contract gross	1,865.6	891.9
Less progress billings	1,948.7	888.5
Net of cost earned on uncompleted contracts	(83.1)	3.4
Costs and recognized earnings in excess of billings on uncompleted contracts	63.7	55.6
Billings in excess of costs and recognized earnings on uncompleted contracts	$ (146.8)	$ (52.2)