Share-Based Compensation (Details) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Summary of stock option activity
Stock Options, Beginning balance	3,776	3,323
Stock Options, Granted	462	894
Stock Options, Exercised	966	395
Stock option, Forfeited/Canceled	52	46
Stock Options, Ending balance	2,181	3,776
Stock Options, Exercisable	1,049
Stock Options, Vested and Expected to Vest	2,151
Weighted-Average Exercise Price, Beginning balance	$ 16.92	$ 16.45
Weighted-Average Exercise Price, Granted	$ 18.94	$ 15.98
Weighted-Average Exercise Price, Exercised	$ 9.87	$ 10.12
Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period	(1,039)
Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price	$ 23.68
Weighted-Average Exercise Price, Forfeited/Canceled	$ 18.91	$ 23.25
Weighted-Average Exercise Price, Ending balance	$ 17.20	$ 16.92
Weighted-Average Exercise Price, Exercisable	$ 17.21
Weighted-Average Exercise Price, Vested and expected to vest	$ 17.22
Weighted-Average Remaining Contractual Term (Years), Outstanding	3 years 37 days	2 years 110 days
Weighted-Average Remaining Contractual Term (Years), Exercisable	1 year 146 days
Weighted-Average Remaining Contractual Term (Years), Vested and expected to vest	3 years 37 days
Aggregate Intrinsic Value, Outstanding	$ 8,399	$ 10,699
Aggregate Intrinsic Value, Exercisable	4,025
Aggregate Intrinsic Value, Vested and expected to vest	$ 8,246

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