Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Income Taxes
Income tax provisions	$ 12.0	$ 6.8	$ 33.5	$ 18.9
Effective tax rate (as a percent)	27.40%	30.40%	26.10%	25.90%
Estimated tax rate for the year before change (as a percent)	31.80%
Estimated tax rate for the year (as a percent)	31.00%
Release of reserves for uncertain tax positions as a result of an audit settlement	1.0		5.5
Effective tax rate excluding audit settlements (as a percent)	31.00%		31.00%
New Clean Energy Manufacturing Tax Credits			$ 3.5
Effective tax rate excluding New Clean Energy Manufacturing Tax Credits (as a percent)			30.70%