Leases - Lease Expense and Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Lease expense
Lease expense	$ 14.3	$ 14.8	$ 14.4
Operating lease expense	5.5	5.6	6.4
Short-term lease expense	0.6	1.5	0.8
Amortization of finance lease right of use assets	4.9
Interest on finance lease liabilities	3.3
Other information
Operating cash flows from finance/capital leases	3.3	7.7	7.2
Operating cash flows from operating leases	6.0	6.5	7.1
Financing cash flows from finance leases	4.9
Right-of-use asset obtained in exchange for finance lease liabilities	27.2
Right of use assets obtained in exchange for operating lease liabilities	$ 49.0
Weighted average remaining lease term - finance leases	31 years 6 months
Weighted average remaining lease term - operating leases	12 years 10 months 24 days
Weighted average discount rate - finance leases	6.70%
Weighted average discount rate - operating leases	4.40%
Finance and capital leases
Lease expense
Lease expense	$ 8.2	$ 7.7	$ 7.2