Commitments and Contingencies - Lease Cost, Cash Flows and Other Supplemental Information - Operating Leases (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 12.1	$ 12.3	$ 35.8	$ 36.6
Sublease income	(0.6)	(0.7)	(1.8)	(1.7)
Total operating lease cost	11.5	11.6	34.0	34.9
Cash paid for amounts included in the measurement of operating lease liabilities	$ 13.4	$ 14.6	$ 42.2	$ 44.7
Weighted-average remaining lease term	9 years 4 months 24 days	9 years 7 months 6 days	9 years 4 months 24 days	9 years 7 months 6 days
Weighted-average discount rate	5.30%	5.30%	5.30%	5.30%