Stockholders' Equity - Summary of Stock Option Activity under the Company's Equity-Based Plans (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Beginning Balance	6,281,148
Number of Shares, Granted	2,448,500
Number of Shares, Exercised	(590,482)
Number of Shares, Forfeited	(66,052)
Number of Shares, Expired	(6,580)
Number of Shares, Ending Balance	8,066,534	6,281,148
Number of Shares, Exercisable, Ending Balance	1,408,826
Number of Shares, Vested and expected to vest, Ending Balance	7,322,533
Weighted-Average Exercise Price, Beginning Balance	$ 1.74
Weighted-Average Exercise Price, Granted	$ 11.20
Weighted-Average Exercise Price, Exercised	$ 0.84
Weighted-Average Exercise Price, Forfeited	$ 2.54
Weighted-Average Exercise Price, Expired	$ 0.50
Weighted-Average Exercise Price, Ending Balance	$ 4.67	$ 1.74
Weighted-Average Exercise Price, Exercisable, Ending Balance	$ 0.79
Weighted-Average Exercise Price, Vested and expected to vest, Ending Balance	$ 3.88
Weighted-Average Remaining Contractual Term (Years)	8 years 9 months 22 days	8 years 6 months 18 days
Weighted-Average Remaining Contractual Term (Years), Exercisable	7 years 7 months 17 days
Weighted-Average Remaining Contractual Term (Years), Vested and Expected to vest	8 years 9 months 4 days
Aggregate Intrinsic Value, Beginning Balance	$ 53,373
Aggregate Intrinsic Value, Ending Balance	134,227	53,373
Aggregate Intrinsic Value, Exercisable, Ending Balance	28,905
Aggregate Intrinsic Value, Vested and expected to Vest, Ending Balance	$ 127,667