Stock-Based Compensation - Additional Information (Detail) - shares |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2017 |
Sep. 30, 2016 |
Sep. 30, 2017 |
Sep. 30, 2016 |
|
| Time-based Restricted Units [Member] | ||||
| Stock Based Compensation [Line Items] | ||||
| Restricted units awarded to managers (shares) | 26,296 | 10,992 | 472,913 | 25,280 |
| Performance-based Restricted Units [Member] | ||||
| Stock Based Compensation [Line Items] | ||||
| Restricted units awarded to managers (shares) | 4,646 | 2,318 | 371,045 | 310,481 |