Condensed Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income (loss)	$ 243.6	$ (80.0)
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments, net	(11.4)	(9.0)
Unrealized gains (losses) on derivative contracts, net	7.0	(17.9)
Amortization of prior service costs and actuarial losses, net	10.6	9.2
Total other comprehensive income (loss), net of tax	6.2	(17.7)
Comprehensive income (loss)	$ 249.8	$ (97.7)