Stock-Based Compensation (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense related to all stock-based compensation plans	$ 7.8	$ 8.8	$ 7.3
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense related to award	1.3	1.7	1.5
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs	2.7
Weighted-average period of years costs are expected to be recognied over	1.1
Compensation expense related to award	$ 2.3	$ 1.9	$ 0.6