Earnings Per Common Share (Computation of Earnings Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings Per Share [Abstract]
Net income to common shareholders	$ 121,435	$ 88,718	$ 244,913	$ 195,890
Net income allocated to participating securities - basic and diluted	1,844	1,894	3,762	4,231
Net income allocated to common shareholders - basic and diluted	$ 119,591	$ 86,824	$ 241,151	$ 191,659
Weighted-average common shares - basic	86,067	86,814	86,362	86,783
Dilutive potential common shares	287	176	292	149
Weighted-average common shares - diluted	86,354	86,990	86,654	86,932
Earnings per common share: Basic	$ 1.39	$ 1.00	$ 2.79	$ 2.21
Earnings per common share: Diluted	$ 1.38	$ 1.00	$ 2.78	$ 2.20