Stockholders' Equity (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Summary of stock option activity
Number of Shares, Outstanding at December 31, 2011	2,130
Weighted Average Exercise Price, Outstanding, Beginning Balance	$ 27.46
Number of Shares, Granted	422
Weighted Average Exercise Price, Granted	$ 33.25
Number of Shares, Exercised	(435)
Weighted Average Exercise Price, Exercised	$ 24.47
Number of Shares, Forfeited	(181)
Weighted Average Exercise Price, Forfeited	$ 31.44
Number of Shares, Outstanding at December 31, 2012	1,936
Weighted Average Exercise Price, Outstanding, Ending Balance	$ 29.03
Weighted Average Remaining Contractual Term, Outstanding	6 years 4 months 13 days
Aggregate Intrinsic Value, Outstanding, Ending Balance	$ 2,319
Number of Shares, Vested and expected to vest at December 31,2012	1,859
Weighted Average Exercise Price Per Share, Vested and expected to vest at December 31,2012	$ 28.86
Weighted Average Remaining Contractual Term, Vested and expected to vest at December 31,2012	6 years 3 months 7 days
Aggregate Intrinsic Value, Vested and expected to vest at December 31,2012	2,316
Number of Shares, Exercisable at December 31, 2012	1,096
Weighted Average Exercise Price Per Share, Exercisable	$ 26.48
Weighted Average Remaining Contractual Term, Exercisable	4 years 8 months 23 days
Aggregate Intrinsic Value, Exercisable	$ 2,151