Leases (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Total minimum future lease payments, leases not yet commenced	$ 8.0
Rent expense, excluding variable and short-term expenses	21.7	$ 21.1
Total rent expense including variable rent and short-term expenses	$ 24.5	$ 23.8	$ 25.2
Minimum
Lessee, Lease, Description [Line Items]
Operating leases, not yet commenced, lease term	4 years
Maximum
Lessee, Lease, Description [Line Items]
Operating leases, not yet commenced, lease term	13 years