Stock-Based Compensation (Details 6) (Restricted Stock Units [Member], USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Restricted Stock Units [Member]
Schedule of information regarding restricted stock units outstanding
RSUs outstanding, Number of Shares	708,651	407,765	417,923	198,055
RSUs outstanding, Weighted Average Remaining Contractual Life (years)	1 year 1 month 2 days	11 months 12 days	1 year 1 month 17 days
RSUs outstanding, Aggregate Intrinsic Value	$ 4.9	$ 2.1	$ 2.8
RSUs outstanding, Fair Value	4.9	2.1	2.8
RSUs vested and expected to vest using estimated forfeiture rates, Number of Shares	588,170	336,454	330,038
RSUs vested and expected to vest, using estimated forfeiture rates, Weighted Average Remaining Contractual Life (years)	1 year 18 days	11 months 1 day	1 year
RSUs vested and expected to vest, using estimated forfeiture rates, Aggregate Intrinsic Value	$ 4.0	$ 1.7	$ 2.2