Earnings Per Common Share - Summary of Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
|
| Numerator for both basic and diluted earnings per common share: | ||
| Net income | $ 33,529 | $ 25,886 |
| Denominator: | ||
| Total average basic common shares outstanding | 44,050,701 | 43,947,563 |
| Effect of dilutive stock options and other stock compensation | 117,541 | 73,202 |
| Total diluted average common shares outstanding | 44,168,242 | 44,020,765 |
| Earnings per common share - basic | $ 0.76 | $ 0.59 |
| Earnings per common share - diluted | $ 0.76 | $ 0.59 |