Stock-Based Compensation Plans - Summary of Performance Unit Awards (Detail) - Performance Unit Awards |
3 Months Ended |
|---|---|
|
Mar. 31, 2018
$ / shares
shares
| |
| Number of Units | |
| Outstanding, beginning balance | shares | 6,851,542 |
| Granted | shares | 3,830,000 |
| Vested | shares | (2,052,959) |
| Forfeited | shares | (10,000) |
| Outstanding, ending balance | shares | 8,618,583 |
| Weighted Average Grant Date Fair Value | |
| Outstanding, beginning balance (in USD per share) | $ / shares | $ 0.81 |
| Granted (in USD per share) | $ / shares | 0.83 |
| Vested (in USD per share) | $ / shares | 0.95 |
| Forfeited (in USD per share) | $ / shares | 0.92 |
| Outstanding, ending balance (in USD per share) | $ / shares | $ 0.79 |