Income Taxes (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary of difference between the income tax provision from continuing operations computed at the statutory federal income tax rate and the financial statement provision for taxes
Provision at the U.S. statutory rate of 35%	$ 45.7	$ 61.8	$ 35.3
Increase (reduction) in tax expense resulting from:
State income tax, net of federal income tax benefit	1.6	2.5	3.8
Other permanent items	(3.3)	(2.3)	(2.8)
Research tax credit	(0.3)	(0.5)	(0.6)
Decrease in tax audit reserves	(0.6)	(0.2)	(1.6)
Change in valuation allowance	(0.5)	(1.8)	4.5
Foreign taxes at rates other than 35% and miscellaneous other	(0.3)		0.5
Total income tax provision	$ 42.3	$ 59.5	$ 39.1