Leases (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Leases
Operating lease cost	$ 20.4	$ 21.1	$ 41.5	$ 41.9
Cash payments for operating leases			41.3	41.4
Right-of-use assets obtained in exchange for operating lease obligations			$ 27.5	$ 28.6
Weighted average remaining lease term - operating leases	5 years 10 months 24 days		5 years 10 months 24 days		5 years 7 months 6 days
Weighted average discount rate - operating leases	4.30%		4.30%		4.30%
Maturities of operating lease liabilities
2020 (remaining six months)	$ 30.6		$ 30.6
2021	52.5		52.5
2022	40.9		40.9
2023	31.9		31.9
2024	24.9		24.9
Thereafter	51.2		51.2
Total operating lease payments	232.0		232.0
Less: imputed interest	(30.7)		(30.7)
Total operating lease liabilities	$ 201.3		$ 201.3