| Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] |
| | | | | | | | | | | | | Three Months Ended June 30, 2020 | | Income |
| Shares |
| Per Share
Amount | | (Thousands, except per share amounts) | Basic EPS Calculation | |
| |
| | Net income available for common stock | $ | 25,325 |
|
| 53,053 |
|
| $ | 0.48 |
| Diluted EPS Calculation | |
|
| |
|
| |
| Effect of dilutive securities | — |
|
| 211 |
|
| |
| Net income available for common stock and common stock equivalents | $ | 25,325 |
|
| 53,264 |
|
| $ | 0.48 |
|
| | | | | | | | | | | | | Three Months Ended June 30, 2019 | | Income | | Shares | | Per Share Amount | | (Thousands, except per share amounts) | Basic EPS Calculation | | | | | | Net income available for common stock | $ | 24,470 |
| | 52,890 |
| | $ | 0.46 |
| Diluted EPS Calculation | | | |
| | |
| Effect of dilutive securities | — |
| | 325 |
| | |
| Net income available for common stock and common stock equivalents | $ | 24,470 |
| | 53,215 |
| | $ | 0.46 |
|
| | | | | | | | | | | | | Six Months Ended June 30, 2020 | | Income | | Shares | | Per Share
Amount | | (Thousands, except per share amounts) | Basic EPS Calculation | | | | | | Net income available for common stock | $ | 117,002 |
| | 53,030 |
| | $ | 2.21 |
| Diluted EPS Calculation | |
| | |
| | |
| Effect of dilutive securities | — |
| | 236 |
| | |
| Net income available for common stock and common stock equivalents | $ | 117,002 |
| | 53,266 |
| | $ | 2.20 |
|
| | | | | | | | | | | | | Six Months Ended June 30, 2019 | | Income | | Shares | | Per Share
Amount | | (Thousands, except per share amounts) | Basic EPS Calculation | | | | | | Net income available for common stock | $ | 118,130 |
| | 52,858 |
| | $ | 2.23 |
| Diluted EPS Calculation | |
| | |
| | |
| Effect of dilutive securities | — |
| | 352 |
| | |
| Net income available for common stock and common stock equivalents | $ | 118,130 |
| | 53,210 |
| | $ | 2.22 |
|
|