Stock-Based Compensation (Details 1) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Summary of stock option activity
Outstanding at December 31, 2011	2,182,940
Granted	193,500
Cancelled/forfeited
Exercised	(322,443)
Outstanding at September 30, 2012	2,053,997
Exercisable at September 30, 2012	1,644,169
Weighted Average Exercise Price, Outstanding at December 31, 2011	$ 13.00
Weighted Average Exercise Price, Granted	$ 22.17
Weighted Average Exercise Price, Cancelled/forfeited
Weighted Average Exercise Price, Exercised	$ 4.52
Weighted Average Exercise Price, Outstanding at September 30, 2012	$ 15.19
Weighted Average Exercise Price, Exercisable at September 30, 2012	$ 13.49
Aggregate Intrinsic Value, Outstanding at September 30, 2012	$ 26,837
Aggregate Intrinsic Value, Exercisable at September 30, 2012	$ 24,282
Minimum [Member]
Summary of stock option activity
Option Price Per Share, Outstanding at December 31, 2011	$ 0.51
Option Price Per Share, Granted
Option Price Per Share, Cancelled/forfeited
Option Price Per Share, Exercised	$ 0.51
Option Price Per Share, Outstanding at September 30, 2012	$ 1.30
Option Price Per Share, Exercisable at September 30, 2012	$ 1.30
Maximum [Member]
Summary of stock option activity
Option Price Per Share, Outstanding at December 31, 2011	$ 24.65
Option Price Per Share, Granted	$ 22.17
Option Price Per Share, Cancelled/forfeited
Option Price Per Share, Exercised	$ 20.09
Option Price Per Share, Outstanding at September 30, 2012	$ 24.65
Option Price Per Share, Exercisable at September 30, 2012	$ 24.65