Fair Value Measurements - Reconciliation of Company's Liabilities Measured at Fair Value on Recurring Basis Using Unobservable Inputs (Level 3) (Detail) - Significant Unobservable Inputs (Level 3) [Member]
$ in Thousands |
12 Months Ended |
|
Dec. 31, 2014
USD ($)
|
|---|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
| Preferred stock warrant liability, Beginning balance |
$ 928
|
| Fair value reclassified to additional paid-in capital in connection with the completion of the IPO on April 15, 2014 |
(928)
|
| Preferred Stock Warrant, Series B [Member] |
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
| Preferred stock warrant liability, Beginning balance |
4
|
| Fair value reclassified to additional paid-in capital in connection with the completion of the IPO on April 15, 2014 |
(4)
|
| Preferred Stock Warrant, Series C [Member] |
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
| Preferred stock warrant liability, Beginning balance |
386
|
| Fair value reclassified to additional paid-in capital in connection with the completion of the IPO on April 15, 2014 |
(386)
|
| Preferred Stock Warrant, Series D [Member] |
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
| Preferred stock warrant liability, Beginning balance |
538
|
| Fair value reclassified to additional paid-in capital in connection with the completion of the IPO on April 15, 2014 |
$ (538)
|