Investments and Fair Value of Financial Instruments - Fair Value Hierarchy for its Financial Assets and Liabilities (Detail) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Cash and cash equivalents: | ||
| Total financial assets | $ 11,126 | $ 24,116 |
| Money market funds [Member] | ||
| Cash and cash equivalents: | ||
| Total financial assets | 11,126 | 24,116 |
| Level I [Member] | ||
| Cash and cash equivalents: | ||
| Total financial assets | 11,126 | 24,116 |
| Level I [Member] | Money market funds [Member] | ||
| Cash and cash equivalents: | ||
| Total financial assets | $ 11,126 | $ 24,116 |