| Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Earnings per share – basic: | | | | | | | | | | | | | | | | | | Net income | | $ | 17,556 | | | $ | 48,847 | | | $ | 34,958 | | | $ | 64,710 | | | Income allocated to participating securities | | | (18 | ) | | | (41 | ) | | | (34 | ) | | | (50 | ) | | Income available to common shareholders | | $ | 17,538 | | | $ | 48,806 | | | $ | 34,924 | | | $ | 64,660 | | | Weighted-average shares outstanding – basic | | | 37,766 | | | | 37,449 | | | | 37,732 | | | | 37,412 | | | Earnings per share – basic | | $ | 0.46 | | | $ | 1.30 | | | $ | 0.93 | | | $ | 1.73 | | | | | | | | | | | | | | | | | | | | | Earnings per share – diluted: | | | | | | | | | | | | | | | | | | Net income | | $ | 17,556 | | | $ | 48,847 | | | $ | 34,958 | | | $ | 64,710 | | | Income allocated to participating securities | | | (18 | ) | | | (41 | ) | | | (34 | ) | | | (50 | ) | | Income available to common shareholders | | $ | 17,538 | | | $ | 48,806 | | | $ | 34,924 | | | $ | 64,660 | | | Weighted-average shares outstanding – basic | | | 37,766 | | | | 37,449 | | | | 37,732 | | | | 37,412 | | | Dilutive effect of stock options and restricted stock units | | | 982 | | | | 477 | | | | 1,050 | | | | 404 | | | Weighted-average common shares outstanding – diluted | | | 38,748 | | | | 37,926 | | | | 38,782 | | | | 37,816 | | | Earnings per share – diluted | | $ | 0.45 | | | $ | 1.29 | | | $ | 0.90 | | | $ | 1.71 | | |