Stock-Based Compensation (Details 3) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of information regarding stock options outstanding
Options outstanding, Number of Shares	3,738,174	3,155,631	3,267,838
Options outstanding, Weighted Average Exercise Price	$ 7.33	$ 6.65
Options outstanding, Weighted Average Remaining Contractual Life (years)	5 years 7 months 2 days	5 years 2 months 27 days
Options outstanding, Aggregate Intrinsic Value	$ 17.2	$ 3.5
Options vested and expected to vest using estimated forfeiture rates, Number of Shares	3,445,934	3,019,979
Options vested and expected to vest using estimated forfeiture rates, Weighted Average Exercise Price	$ 7.24	$ 6.67
Options vested and expected to vest using estimated forfeiture rates, Weighted Average Remaining Contractual Life (years)	5 years 5 months 27 days	5 years 2 months 1 day
Options vested and expected to vest using estimated forfeiture rates, Aggregate Intrinsic Value	16.2	3.4
Options exercisable, Number of Shares	2,123,986	2,329,987
Options exercisable, Weighted Average Exercise Price	$ 6.90	$ 6.91
Options exercisable, Weighted Average Remaining Contractual Life (years)	4 years 8 months 16 days	4 years 8 months 9 days
Options exercisable, Aggregate Intrinsic Value	$ 11.0	$ 2.5