Earnings Per Share (Computation of Earnings Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Earnings Per Share [Abstract]
Net income to common shareholders	$ 392,602	$ 524,089	$ 463,215
Net income or dividends allocated to participating securities - basic and diluted	4,014	7,620	9,134
Net income allocated to common shareholders - basic	388,588	516,469	454,081
Net income allocated to common shareholders - diluted	$ 388,588	$ 516,469	$ 454,081
Weighted-average common shares - basic	86,130	86,068	86,823
Dilutive potential common shares	293	326	204
Weighted average common shares - diluted	86,423	86,394	87,027
Earnings per common share: Basic	$ 4.51	$ 6	$ 5.23
Earnings per common share: Diluted	$ 4.5	$ 5.98	$ 5.22