Leases - Supplemental Income Statement Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating lease cost:
Operating lease cost	$ 6.0	$ 8.6
Short-term lease cost	3.4	9.9
Variable lease cost	0.5	1.0
Sublease income	(0.5)	0.0
Total operating lease cost	9.4	19.5
Finance lease cost:
Amortization of right-of-use assets	0.6	3.4
Interest on lease liabilities	0.5	0.2
Total finance lease cost	$ 1.1	$ 3.6