| Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Earnings per share – basic: | | | | | | | | | | | | | | | | | | Net income | | $ | 44,654 | | | $ | 19,738 | | | $ | 79,612 | | | $ | 84,449 | | | Income allocated to participating securities | | | (35 | ) | | | (18 | ) | | | (66 | ) | | | (70 | ) | | Income available to common shareholders | | $ | 44,619 | | | $ | 19,720 | | | $ | 79,546 | | | $ | 84,379 | | | Weighted-average shares outstanding – basic | | | 37,772 | | | | 37,503 | | | | 37,745 | | | | 37,450 | | | Earnings per share – basic | | $ | 1.18 | | | $ | 0.53 | | | $ | 2.11 | | | $ | 2.25 | | | | | | | | | | | | | | | | | | | | | Earnings per share – diluted: | | | | | | | | | | | | | | | | | | Net income | | $ | 44,654 | | | $ | 19,738 | | | $ | 79,612 | | | $ | 84,449 | | | Income allocated to participating securities | | | (35 | ) | | | (18 | ) | | | (66 | ) | | | (70 | ) | | Income available to common shareholders | | $ | 44,619 | | | $ | 19,720 | | | $ | 79,546 | | | $ | 84,379 | | | Weighted-average shares outstanding – basic | | | 37,772 | | | | 37,503 | | | | 37,745 | | | | 37,450 | | | Dilutive effect of stock options and restricted stock units | | | 1,089 | | | | 639 | | | | 1,068 | | | | 483 | | | Weighted-average common shares outstanding – diluted | | | 38,861 | | | | 38,142 | | | | 38,813 | | | | 37,933 | | | Earnings per share – diluted | | $ | 1.15 | | | $ | 0.52 | | | $ | 2.05 | | | $ | 2.22 | | |