Stockholders' Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Summary of stock option activity
Number of Shares, Outstanding-December 31, 2012	8,251,850
Number Of Shares, Assumed Options From Acquisition	9,182
Number of Shares, Granted	710,381
Number of Shares, Exercised	(2,170,457)
Number of Shares, Canceled or expired	(166,991)
Number of Shares, Outstanding-June 30, 2013	6,633,965
Number of Shares, Options vested and expected to vest as of June 30, 2013	6,306,705
Number of Shares, Options vested and exercisable as of June 30, 2013	3,281,054
Weighted- Average Exercise Price, Outstanding-December 31, 2012	$ 10.50
Weighted Average Exercise Price, Assumed Options From Acquisition	$ 14.50
Weighted- Average Exercise Price, Granted	$ 170.02
Weighted- Average Exercise Price, Exercised	$ 9.10
Weighted- Average Exercise Price, Canceled or expired	$ 12.34
Weighted- Average Exercise Price, Outstanding-June 30, 2013	$ 28.00
Weighted- Average Exercise Price, Options vested and expected to vest as of June 30, 2013	$ 25.00
Weighted- Average Exercise Price, Options vested and exercisable as of June 30, 2013	$ 6.59
Weighted average remaining contractual term, outstanding	6 years 11 months 12 days
Weighted average remaining contractual term, options vested and expected to vest	6 years 10 months 13 days
Weighted average remaining contractual, options vested and exercisable	6 years 0 months 14 days
Aggregate Intrinsic Value, Outstanding-June 30, 2013	$ 997,105
Aggregate Intrinsic Value, Options vested and expected to vest as of June 30, 2013	966,837
Aggregate Intrinsic Value, Options vested and exercisable as of June 30, 2013	$ 563,399