Fair Value Measurements - Schedule of Fair Value Financial Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($)
$ in Thousands |
Jun. 30, 2015 |
Dec. 31, 2014 |
| Financial Assets |
|
|
| Total financial assets |
$ 25,466
|
$ 37,932
|
| Preferred Stock Warrant Liabilities [Member] |
|
|
| Financial Liabilities |
|
|
| Total financial Liabilities |
10,641
|
1,810
|
| Money Market Funds [Member] |
|
|
| Financial Assets |
|
|
| Total financial assets |
15,213
|
27,847
|
| Restricted Money Market Funds [Member] |
|
|
| Financial Assets |
|
|
| Total financial assets |
225
|
75
|
| Short-Term Investments [Member] |
|
|
| Financial Assets |
|
|
| Total financial assets |
10,028
|
10,010
|
| Level 1 [Member] |
|
|
| Financial Assets |
|
|
| Total financial assets |
15,438
|
27,922
|
| Level 1 [Member] | Money Market Funds [Member] |
|
|
| Financial Assets |
|
|
| Total financial assets |
15,213
|
27,847
|
| Level 1 [Member] | Restricted Money Market Funds [Member] |
|
|
| Financial Assets |
|
|
| Total financial assets |
225
|
75
|
| Level 2 [Member] |
|
|
| Financial Assets |
|
|
| Total financial assets |
10,028
|
10,010
|
| Level 2 [Member] | Short-Term Investments [Member] |
|
|
| Financial Assets |
|
|
| Total financial assets |
10,028
|
10,010
|
| Level 3 [Member] | Preferred Stock Warrant Liabilities [Member] |
|
|
| Financial Liabilities |
|
|
| Total financial Liabilities |
$ 10,641
|
$ 1,810
|