Stock-Based Compensation (Details 1) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Options
Number of Shares Outstanding (Options), Beginning Balance	2,348,162
Number of Shares Outstanding (Options), Exercised	(281,450)
Number of Shares Outstanding (Options), Granted	200,485
Number of Shares Outstanding (Options), Cancelled	(49,843)
Number of Shares Outstanding (Options), Ending Balance	2,217,354	2,348,162
Number of Shares Outstanding (Options), Exercisable at June 30, 2012	1,206,793
Weighted Average Exercise Price, Beginning Balance	$ 10.53
Weighted Average Exercise Price, Exercised	$ 6.32
Weighted Average Exercise Price, Granted	$ 17.72
Weighted Average Exercise Price, Cancelled	$ 14.53
Weighted Average Exercise Price, Ending Balance	$ 11.62	$ 10.53
Weighted Average Exercise Price, Exercisable at June 30, 2012	$ 9.14
Weighed Average Remaining Contractual Term, Opening	4 years 8 months 9 days	4 years 10 months 10 days
Weighed Average Remaining Contractual Term, Closing	4 years 8 months 9 days	4 years 10 months 10 days
Weighed Average Remaining Contractual Term, Exercisable at June 30, 2012	4 years
Aggregate Intrinsic Value, Opening	$ 18,556
Aggregate Intrinsic Value, Closing	9,587	18,556
Aggregate Intrinsic Value, Exercisable at June 30, 2012	$ 7,781