Condensed Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net (loss) income	$ (120.1)	$ (80.0)	$ (20.0)	$ 41.7	$ (200.1)	$ 21.7
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments, net	8.2		3.3		(0.8)	(5.0)
Unrealized gains (losses) on derivative contracts, net	30.0		(12.1)		12.1	(15.4)
Amortization of prior service costs and actuarial losses, net	9.0		5.3		18.2	11.0
Total other comprehensive income (loss), net of tax	47.2	$ (17.7)	(3.5)	$ (5.9)	29.5	(9.4)
Comprehensive (loss) income	$ (72.9)		$ (23.5)		$ (170.6)	$ 12.3