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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 14.1	$ 12.1	$ 41.6	$ 35.8
Sublease income	(1.0)	(0.6)	(2.2)	(1.8)
Total operating lease cost	13.1	11.5	39.4	34.0
Cash paid for amounts included in the measurement of operating lease liabilities	$ 12.4	$ 13.4	$ 35.1	$ 42.2
Weighted-average remaining lease term	12 years 1 month 6 days	9 years 4 months 24 days	12 years 1 month 6 days	9 years 4 months 24 days
Weighted-average discount rate	4.10%	5.30%	4.10%	5.30%