Net Income (Loss) Per Share - Schedule of Securities Excluded from Calculation of Net Loss Per Share (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive excluded from computation of earnings per share amount (shares)	0	14,122,848	10,550,888	13,950,591
2018 Convertible Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive excluded from computation of earnings per share amount (shares)	0	10,454,799	3,854,959	10,454,799
Common stock options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive excluded from computation of earnings per share amount (shares)	0	1,271,207	4,396,587	1,110,474
Restricted stock awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive excluded from computation of earnings per share amount (shares)	0	2,166,299	1,797,089	2,166,299
Restricted stock units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive excluded from computation of earnings per share amount (shares)	0	217,206	245,214	217,206
Common Stock Warrant [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive excluded from computation of earnings per share amount (shares)	0	13,337	257,039	1,813