Share-Based Payments (Tables)

12 Months Ended

Dec. 31, 2013

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Award Activity

 These awards are included within the following table which summarizes the activity of the 2007 Plan and the 2013 Plan for the year ended December 31, 2013. Also included in the following table are 313,634 of options subject to performance conditions deemed not probable of achievement as of December 31, 2013: 

	Number of Stock Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2012		3,145,544		$	0.88		7.72	$	15,402
Granted		986,294			13.59
Exercised		(237,565	)		0.63
Forfeited/Expired		(48,105	)		1.99
Outstanding at December 31, 2013		3,846,168		$	4.14		7.43	$	76,189
Exercisable at December 31, 2013		2,161,333		$	0.61		6.34	$	50,443
Vested and expected to vest at December 31, 2013		3,278,066		$	3.33		7.15	$	67,604

Restricted Stock Activity

Restricted stock activity for the year ended December 31, 2013 is summarized as follows:

Unvested shares at December 31, 2012	160,053
Granted	—
Vested	(136,758	)
Forfeited	—
Unvested shares at December 31, 2013	23,295

Schedule of Fair Value Option Award Weighted Average Assumptions Used

 The following table summarizes the weighted average assumptions used in calculating the fair value of the awards:

	Years Ending December 31,
	2013			2012			2011
Risk-free interest rate		1.31	%		1.09	%		1.97	%
Expected dividend yield		—			—			—
Expected term (in years)		6.42			6.08			6.09
Expected volatility		92.49	%		97.75	%		98.60	%