Summary of Significant Accounting Policies - Reconciliations of Numerators and Denominators of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands |
3 Months Ended | 12 Months Ended | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2017 |
Sep. 30, 2017 |
Jun. 30, 2017 |
Mar. 31, 2017 |
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, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Earnings Per Share [Abstract] | |||||||||||||||
| Net loss | $ 45,817 | $ (8,512) | $ (8,896) | $ (140,768) | $ (13,475) | $ (9,073) | $ (16,035) | $ (13,660) | $ (5,759) | $ (148,787) | $ (11,850) | $ (7,708) | $ (112,359) | $ (52,243) | $ (174,104) |
| Weighted average shares — basic | 83,404,104 | 41,488,206 | 40,464,283 | ||||||||||||
| Weighted average shares — diluted | 83,404,104 | 41,488,206 | 40,464,283 | ||||||||||||
| Basic | $ 0.51 | $ (0.10) | $ (0.10) | $ (2.00) | $ (0.32) | $ (0.22) | $ (0.39) | $ (0.33) | $ (0.14) | $ (3.67) | $ (0.29) | $ (0.19) | $ (1.35) | $ (1.26) | $ (4.30) |
| Diluted | $ 0.51 | $ (0.10) | $ (0.10) | $ (2.00) | $ (0.32) | $ (0.22) | $ (0.39) | $ (0.33) | $ (0.14) | $ (3.67) | $ (0.29) | $ (0.19) | $ (1.35) | $ (1.26) | $ (4.30) |