Commitments and Contingencies - Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 50.8	$ 50.3
Variable lease cost	13.4	12.6
Total lease cost	64.2	62.9
Operating cash outflows from operating leases	54.2	49.6
ROU assets obtained in exchange for new operating lease liabilities	$ 54.7	$ 14.0
Weighted average remaining lease term (years)	4 years 10 months 24 days	5 years 6 months
Weighted average discount rate	3.70%	3.90%