Stock-based compensation and warrants - Summary of Stock Option Activity Under Plan (Detail) - Jun. 30, 2015 - $ / shares shares in Thousands	Total
Shares
Outstanding at beginning of period	3,652
Granted	915
Exercised	(671)
Canceled or forfeited	(43)
Outstanding at end of period	3,853
Exercisable at end of period	1,325
Vested and expected to vest at end of period	3,776
Weighted-average exercise price per share
Outstanding at beginning of period	$ 12.30
Granted	106.87
Exercised	7.97
Canceled or forfeited	44.68
Outstanding at end of period	35.15
Exercisable at end of period	7.89
Vested and expected to vest at end of period	$ 35.61