Earnings Per Common Share (Computation of Earnings Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Earnings Per Share [Abstract]
Net income to common shareholders	$ 126,467	$ 123,478
Net income allocated to participating securities - basic and diluted	1,358	1,918
Net income allocated to common shareholders - basic and diluted	$ 125,109	$ 121,560
Weighted-average common shares - basic	86,018	86,660
Dilutive potential common shares	264	276
Weighted-average common shares - diluted	86,282	86,936
Earnings per common share: Basic	$ 1.45	$ 1.40
Earnings per common share: Diluted	$ 1.45	$ 1.40