Leases - Supplemental Income Statement Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating lease cost:
Operating lease cost	$ 4.6	$ 6.3	$ 15.3	$ 23.3
Short-term lease cost	4.1	10.2	10.5	31.7
Variable lease cost	1.0	1.1	2.0	3.7
Sublease income	(0.5)	0.0	(1.5)	0.0
Total operating lease cost	9.2	17.6	26.3	58.7
Finance lease cost:
Amortization of right-of-use assets	1.6	0.8	3.7	5.2
Interest on lease liabilities	0.8	0.2	2.0	0.5
Total finance lease cost	$ 2.4	$ 1.0	$ 5.7	$ 5.7