Leases (Operating Leases) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2020	$ 41.7
2021	37.9
2022	25.4
2023	22.9
2024	17.7
Thereafter	55.7
Total lease payments	201.3
Adjustment for discount to present value	26.8
Total lease liabilities	$ 174.5
Deferred rent	6 years 7 months 6 days
Operating lease expense	$ 33.9	$ 32.5	$ 30.3
Variable operating lease charges	12.7
Payments on operating leases	$ 33.1
Operating Lease, Weighted Average Discount Rate, Percent	4.20%
Lease not yet commenced	$ 16.7