Stock-Based Compensation - Summary of Restricted Stock Unit Activity and Related Information (Detail) - Restricted Stock Units (RSUs) [Member] - $ / shares
|
12 Months Ended |
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
|
| Number of Restricted Stock Units, Outstanding, Beginning balance |
1,069,100
|
1,889,267
|
2,449,346
|
| Number of Restricted Stock Units, Granted |
933,552
|
455,776
|
460,112
|
| Number of Restricted Stock Units, Vested/issued |
(732,720)
|
(1,032,979)
|
(1,013,446)
|
| Number of Restricted Stock Units, Forfeited / Expired |
(68,773)
|
(242,964)
|
(6,745)
|
| Number of Restricted Stock Units, Outstanding, Ending balance |
1,201,159
|
1,069,100
|
1,889,267
|
| Weighted Average Fair Value, Beginning Balance |
$ 1.55
|
$ 1.70
|
$ 1.71
|
| Number of Restricted Stock Units, Vested/Issued Cumulative |
3,257,323
|
|
|
| Weighted Average Fair Value, Granted |
$ 2.19
|
1.28
|
1.65
|
| Weighted Average Fair Value, Vested/Issued |
1.71
|
1.69
|
1.71
|
| Weighted Average Fair Value, Forfeited/Expired |
1.90
|
1.62
|
1.68
|
| Weighted Average Fair Value, Ending Balance |
1.92
|
$ 1.55
|
$ 1.70
|
| Weighted Average Fair Value Vested and Exercisable |
$ 1.71
|
|
|