Condensed Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income	$ 47.6	$ 42.1	$ 86.3	$ 175.8
Other comprehensive income, net of tax:
Foreign currency translation adjustments	(0.8)	1.0	(0.5)	2.3
Unrealized (losses) gains on derivative contracts	(3.0)	(3.1)	1.3	(6.2)
Amortization of prior service costs and actuarial losses	4.3	3.3	7.5	6.1
Total other comprehensive income, net of tax	0.5	1.2	8.3	2.2
Comprehensive income	$ 48.1	$ 43.3	$ 94.6	$ 178.0