Leases - Lease Expense and Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Lease expense
Amortization of finance lease right of use assets	$ 8.1	$ 6.3	$ 4.9
Interest on finance lease liabilities	1.6	2.5	3.3
Operating lease expense	3.4	5.4	5.5
Short-term lease expense	0.2	0.3	0.6
Lease expense	13.3	14.5	14.3
Other information
Operating cash flows from finance leases	1.6	2.5	3.3
Operating cash flows from operating leases	5.3	6.7	6.0
Financing cash flows from finance leases	8.1	6.3	4.9
Right-of-use asset obtained in exchange for finance lease liabilities	73.6	22.8	27.2
Right of use assets obtained in exchange for operating lease liabilities	$ 0.5	$ 0.0	$ 49.0
Weighted average remaining lease term - finance leases	20 years 6 months	41 years 6 months	31 years 6 months
Weighted average remaining lease term - operating leases	12 years 6 months	13 years	12 years 10 months 24 days
Weighted average discount rate - finance leases	2.40%	4.90%	6.70%
Weighted average discount rate - operating leases	3.40%	3.40%	4.40%