Short-Term Marketable Securities - Summary of Short-Term Marketable Securities (Detail) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Schedule of Available-for-sale Securities [Line Items] | ||
| Amortized Cost | $ 30,570 | $ 23,266 |
| Unrealized Gain | 0 | 0 |
| Unrealized Loss | 18 | 8 |
| Market Value | 30,552 | 23,258 |
| U.S. treasuries [Member] | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Amortized Cost | 23,295 | 7,027 |
| Unrealized Gain | 0 | 0 |
| Unrealized Loss | 18 | 8 |
| Market Value | 23,277 | 7,019 |
| Certificates of deposit [Member] | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Amortized Cost | 7,275 | 15,239 |
| Unrealized Gain | 0 | 0 |
| Unrealized Loss | 0 | 0 |
| Market Value | $ 7,275 | 15,239 |
| Corporate bonds [Member] | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Amortized Cost | 1,000 | |
| Unrealized Gain | 0 | |
| Unrealized Loss | 0 | |
| Market Value | $ 1,000 |