Accounting Policies - Instruments Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | |||
| Total | 12,330,914 | 10,931,742 | 14,582,724 |
| Stock Options [Member] | |||
| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | |||
| Total | 9,236,228 | 7,052,642 | 6,383,457 |
| Restricted Stock Units [Member] | |||
| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | |||
| Total | 1,201,159 | 1,069,100 | 1,889,267 |
| Warrants [Member] | |||
| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | |||
| Total | 1,893,527 | 2,810,000 | 6,310,000 |