Stock Option Additional Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value, Total		$ 1.5	$ 8.0
Total intrinsic value of options exercised			14.3
Total fair value of options vested	$ 0.3		$ 8.0