Net Income Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2016 |
Sep. 30, 2015 |
Sep. 30, 2016 |
Sep. 30, 2015 |
|
| Computation of basic and diluted net income per common share | ||||
| Net income | $ 27,296 | $ 33,647 | $ 79,487 | $ 61,726 |
| Net income per common share - basic (in dollars per share) | $ 0.57 | $ 0.71 | $ 1.66 | $ 1.30 |
| Net income per common share - diluted (in dollars per share) | $ 0.55 | $ 0.69 | $ 1.61 | $ 1.27 |
| Weighted average common shares outstanding - basic | 48,049,000 | 47,674,000 | 47,993,000 | 47,466,000 |
| Plus dilutive effect of potential common shares | 1,361,000 | 1,304,000 | 1,294,000 | 1,271,000 |
| Weighted average common shares outstanding - diluted | 49,410,000 | 48,978,000 | 49,287,000 | 48,737,000 |
| Common stock excluded from calculation of EPS | 11 | 18 | 12 | |