Net Income (Loss) Per Share - Number of Outstanding Stock Options, Warrants to Purchase Common Preferred Stock and Convertible Redeemable Preferred Stock Excluded from Computation of Diluted Net Income (Loss) Per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common equivalent shares from stock warrants	0	2,304,931	0	0
Excluded From Earnings Per Share Calculation
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Stock options outstanding	10,328,593	5,817,422	8,876,984	7,229,252
Restricted stock units and restricted stock awards	2,574,405	489,060	1,888,205	556,606
Common equivalent shares from stock warrants	2,168,299	0	2,210,012	2,340,061
Shares purchased under ESPP	54,271	0	67,858	13,088
Antidilutive securities excluded from computation of earnings per share, amount, total	15,125,568	6,306,482	13,043,059	10,139,007