Stock-Based Compensation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1.6	$ 1.3	$ 4.3	$ 4.8
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost			0.8
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs	3.9		3.9
Weighted-average period of years costs are expected to be recognied over			1.6
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost			$ 1.6