Revenue - Contracts and Liabilities (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($)
Contract With Customer, Asset [Roll Forward]
Contract assets, December 31, 2020	$ 10.9
Contract assets, March 31, 2021	12.5
Change in contract assets - increase (decrease)	1.6
Contract With Customer, Liability [Roll Forward]
Deferred income, December 31, 2020	(57.1)
Deferred income, March 31, 2021	(45.1)
Change in deferred income - decrease (increase)	$ 12.0