Quarterly Financial Data - Quarterly Financial Data (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 |
|
| Net Income (Loss) Available to Common Stockholders, Basic [Abstract] | |||||||||||
| Revenues | $ 983 | $ 311 | $ 595 | $ 15,458 | $ 10,605 | $ 396 | $ 216 | $ 731 | $ 17,347 | $ 11,948 | $ 1,623 |
| Net income (loss) | $ (7,127) | $ (6,004) | $ (6,956) | $ 4,750 | $ 3,592 | $ (6,497) | $ (1,035) | $ (12,482) | $ (15,337) | $ (16,422) | $ (22,082) |
| Basic net income (loss) per common share | $ (0.08) | $ (0.07) | $ (0.08) | $ 0.06 | $ 0.04 | $ (0.08) | $ 0.01 | $ (0.16) | $ (0.18) | $ (0.20) | $ (0.29) |
| Diluted net income (loss) per common share | $ (0.10) | $ (0.07) | $ (0.08) | $ 0.06 | $ 0.04 | $ (0.08) | $ (0.05) | $ (0.16) | $ (0.18) | $ (0.20) | $ (0.31) |