Summary of (Unaudited) Quarterly Financial Information - Summary of Company's (Unaudited) Quarterly Results of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2016 |
Sep. 30, 2016 |
Jun. 30, 2016 |
Mar. 31, 2016 |
Dec. 31, 2015 |
Sep. 30, 2015 |
Jun. 30, 2015 |
Mar. 31, 2015 |
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
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| Quarterly Financial Information Disclosure [Abstract] | |||||||||||
| Total revenues | $ 3,163 | $ 2,642 | $ 4,122 | $ 4,604 | $ 6,813 | $ 5,017 | $ 4,176 | $ 4,944 | $ 14,531 | $ 20,950 | $ 15,217 |
| Total operating expenses | 5,938 | 5,213 | 5,443 | 7,114 | 9,235 | 5,350 | 6,968 | 8,801 | 23,708 | 30,354 | 31,843 |
| Net income (loss) | $ (2,772) | $ (2,523) | $ (1,255) | $ (2,423) | $ (2,355) | $ (300) | $ (2,762) | $ (3,821) | $ (8,973) | $ (9,238) | $ (16,492) |
| Basic and diluted net loss per share | $ (0.25) | $ (0.24) | $ (0.14) | $ (0.26) | $ (0.26) | $ (0.03) | $ (0.30) | $ (0.42) | $ (0.90) | $ (1.01) | $ (1.86) |