Stock-based compensation (Tables)

12 Months Ended

Dec. 31, 2012

Stock-based compensation

Summary of restricted stock unit activity and related information

	Shares		Weighted-average purchase price per share
Unvested at December 31, 2011		2,319,646	$	0.002
Granted		—
Vested		674,505	$	0.002
Unvested at December 31, 2012		1,645,141	$	0.002

Summary of the Company's stock option activity and related information

A summary of the Company's stock option activity and related information is as follows (in thousands, except share and per share data):

	Shares			Weighted average exercise price per share		Weighted average remaining contractual term (years)		Aggregate intrinsic value
Outstanding at December 31, 2011		617,633			0.04		9.80	$	2,162
Granted		718,936			6.49
Exercised		(5,792	)		0.04
Forfeited		(112,624	)		0.26
Outstanding at December 31, 2012		1,218,153			3.83		9.34		5,535
Exercisable at December 31, 2012		175,814			0.44		8.84		1,394
Vested and expected to vest at December 31, 2012		1,114,651			3.78		8.84		5,123

Summary of the Company's restricted stock activity and related information

	Shares		Weighted-average grant date fair value
Unvested at December 31, 2011		—		—
Granted		192,308	$	7.80
Vested		—		—
Unvested at December 31, 2012		192,308	$	7.80

Schedule of assumptions used to estimate fair value of each stock-based award on the grant date using the Black-Scholes option pricing model

	December 31, 2012	December 31, 2011
Risk-free interest rate	0.8% - 1.78%	1.2% - 1.84%
Dividend yield	—	—
Volatility	79% - 89%	79% - 82%
Expected term (years)	5.1 - 9.93	6.0 - 9.75

Summary of the status of non-vested RSUs

	Restricted Stock Units		Weighted- Average Grant Date Fair Value		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
Non-vested at December 31, 2011		—	$	—		—
Granted		192,308		7.80		2.00	$	1,500
Vested		—		—		—		—
Cancelled		—		—		—		—
Non-Vested at December 31, 2012		192,308	$	7.80		2.00	$	1,500