Leases (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Leases
Operating lease cost	$ 19.3	$ 20.4	$ 39.0	$ 41.5
Cash payments for operating leases			39.1	41.3
Right-of-use assets obtained in exchange for operating lease obligations			$ 33.0	$ 27.5
Weighted average remaining lease term - operating leases	6 years 2 months 12 days		6 years 2 months 12 days		5 years 8 months 12 days
Weighted average discount rate - operating leases	3.60%		3.60%		3.70%
Maturities of operating lease liabilities
2021 (remaining six months)	$ 29.4		$ 29.4
2022	51.6		51.6
2023	41.9		41.9
2024	33.7		33.7
2025	23.9		23.9
Thereafter	60.5		60.5
Total operating lease payments	241.0		241.0
Less: imputed interest	(30.3)		(30.3)
Total operating lease liabilities	$ 210.7		$ 210.7