Condensed Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income	$ 29.5	$ 40.5
Other comprehensive income, net of tax:
Foreign currency translation adjustments	0.7	0.1
Unrealized losses on derivative contracts	(3.1)	(5.1)
Amortization of prior service costs and actuarial losses	4.0	5.2
Total other comprehensive income, net of tax	1.6	0.2
Comprehensive income	$ 31.1	$ 40.7