Earnings Per Share - Additional Information (Detail) - shares |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Stock Options [Member] | |||
| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | |||
| Anti-dilutive shares excluded from calculation of diluted earnings per share | 272,421 | 831,042 | 0 |
| Restricted Shares [Member] | |||
| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | |||
| Anti-dilutive shares excluded from calculation of diluted earnings per share | 201,432 | 354,423 | 256,165 |