Equity - Restricted Stock Units Outstanding (Detail) - shares |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|
| Equity [Abstract] | |||
| Outstanding on January 1, | 85,384 | 142,851 | 109,750 |
| Issued | 145,979 | 34,292 | 114,821 |
| Vested and issued | (87,923) | (80,261) | (69,906) |
| Vested—issued and repurchased for income tax withholding | (12,518) | (8,853) | (4,414) |
| Forfeited | (12,149) | (2,645) | (7,400) |
| Outstanding on December 31 | 118,773 | 85,384 | 142,851 |