Operating Leases (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) lease_renewal_option	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Lessee, Lease, Description [Line Items]
Weighted-average remaining lease term	5 years 8 months 26 days	6 years 4 months 24 days
Number of options to renew | lease_renewal_option	1
Right-of-use asset	$ 275.7
Present value of lease liabilities	319.2	$ 364.8
Impairment expense	17.8
Impairment expense related to right-of-use asset	$ 13.4
Weighted-average discount rate (percent)	3.39%	3.50%
Expected lease obligations	$ 232.5
Expected lease term	15 years
Operating lease expenses	$ 99.5	$ 72.3	$ 53.2
Sublease Income	$ 2.1	$ 0.6	$ 0.4
Minimum
Lessee, Lease, Description [Line Items]
Lease renewal term	1 year
Period for lease termination notice before end of lease term	1 year
Maximum
Lessee, Lease, Description [Line Items]
Lease renewal term	10 years
Period for lease termination notice before end of lease term	8 years 2 months 12 days