Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Calculations for basic and diluted earnings per common share
Net income	$ 74,262	$ 94,301
Preferred stock dividends	(2,875)	(5,207)
Net income available to common equity	71,387	89,094
Common shareholder dividends	(30,372)	(27,661)
Unvested share-based payment awards	(211)	(209)
Undistributed earnings	40,804	61,224
Undistributed earnings allocated to common shareholders	40,548	60,836
Undistributed earnings allocated to unvested share-based payment awards	256	387
Undistributed earnings	40,804	61,224
Basic
Distributed earnings to common shareholders	30,372	27,661
Undistributed earnings allocated to common shareholders	40,548	60,836
Total common shareholders earnings, basic	70,920	88,497
Diluted
Distributed earnings to common shareholders	30,372	27,661
Undistributed earnings allocated to common shareholders	40,548	60,836
Total common shareholders earnings, diluted	$ 70,920	$ 88,497
Weighted average common shares outstanding	148,781	152,355
Effect of dilutive common stock awards	1,711	1,333
Diluted weighted average common shares outstanding	150,492	153,688
Basic earnings per common share	$ 0.48	$ 0.58
Diluted earnings per common share	$ 0.47	$ 0.58