Condensed Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Condensed Statements of Comprehensive Income
Net income	$ 38.7	$ 133.7
Other comprehensive income, net of tax:
Foreign currency translation adjustments	0.3	1.3
Unrealized gains (losses) on derivative contracts	4.3	(3.1)
Amortization of prior service costs and actuarial losses	3.2	2.8
Other comprehensive income	7.8	1.0
Comprehensive income	$ 46.5	$ 134.7