Earnings Per Common Share (Computation of Earnings Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Earnings Per Share [Abstract]
Net income to common shareholders	$ 135,389	$ 129,582	$ 380,302	$ 325,472
Net income allocated to participating securities - basic and diluted	2,014	2,419	5,776	6,650
Net income allocated to common shareholders - basic and diluted	$ 133,375	$ 127,163	$ 374,526	$ 318,822
Weighted-average common shares - basic	85,706	86,834	86,141	86,800
Dilutive potential common shares	314	172	298	151
Weighted-average common shares - diluted	86,020	87,006	86,439	86,951
Earnings per common share: Basic	$ 1.56	$ 1.46	$ 4.35	$ 3.67
Earnings per common share: Diluted	$ 1.55	$ 1.46	$ 4.33	$ 3.67