Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Preferred Stock	Common Stock	Capital Surplus	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Treasury Stock
Balance at Beginning of Period at Dec. 31, 2019	$ 1,286,832	$ 3,632		$ 579	$ 582,566	$ (31,112)	$ 1,761,415	$ 3,632	$ (1,026,616)
Beginning Balance (in shares) at Dec. 31, 2019				40,039,695
Increase (decrease) in shareholders' equity
Net Income	34,742						34,742
Other Comprehensive Income (Loss)	$ 41,933					41,933
Accounting Standards Update Extensible List	Accounting Standards Update 2016-13
Share-Based Compensation	$ 1,497				1,497
Common Stock Issued under Purchase and Equity Compensation Plans	3,761				329		653		2,779
Common Stock Issued under Purchase and Equity Compensation Plans and Related Tax Benefits (in shares)				154,091
Common Stock Repurchased	(17,633)								(17,633)
Common Stock Repurchased (in shares)				(197,276)
Cash Dividends Declared Common Stock (per share)	(26,835)						(26,835)
Balance at End of Period at Mar. 31, 2020	1,327,929			$ 579	584,392	10,821	1,773,607		(1,041,470)
Ending Balance (in shares) at Mar. 31, 2020				39,996,510
Balance at Beginning of Period at Dec. 31, 2019	1,286,832	$ 3,632		$ 579	582,566	(31,112)	1,761,415	$ 3,632	(1,026,616)
Beginning Balance (in shares) at Dec. 31, 2019				40,039,695
Increase (decrease) in shareholders' equity
Net Income	111,490
Other Comprehensive Income (Loss)	45,511					45,511
Balance at End of Period at Sep. 30, 2020	1,361,739			$ 580	588,632	14,399	1,797,763		(1,039,635)
Ending Balance (in shares) at Sep. 30, 2020				40,060,675
Balance at Beginning of Period at Mar. 31, 2020	1,327,929			$ 579	584,392	10,821	1,773,607		(1,041,470)
Beginning Balance (in shares) at Mar. 31, 2020				39,996,510
Increase (decrease) in shareholders' equity
Net Income	38,908						38,908
Other Comprehensive Income (Loss)	8,104					8,104
Share-Based Compensation	2,207				2,207
Common Stock Issued under Purchase and Equity Compensation Plans	1,926			$ 1	347		680		898
Common Stock Issued under Purchase and Equity Compensation Plans and Related Tax Benefits (in shares)				53,672
Common Stock Repurchased	(148)								(148)
Common Stock Repurchased (in shares)				(2,488)
Cash Dividends Declared Common Stock (per share)	(26,844)						(26,844)
Balance at End of Period at Jun. 30, 2020	1,352,082			$ 580	586,946	18,925	1,786,351		(1,040,720)
Ending Balance (in shares) at Jun. 30, 2020				40,047,694
Increase (decrease) in shareholders' equity
Net Income	37,840						37,840
Other Comprehensive Income (Loss)	(4,526)					(4,526)
Share-Based Compensation	1,643				1,643
Common Stock Issued under Purchase and Equity Compensation Plans	1,673				43		429		1,201
Common Stock Issued under Purchase and Equity Compensation Plans and Related Tax Benefits (in shares)				14,919
Common Stock Repurchased	(116)								(116)
Common Stock Repurchased (in shares)				(1,938)
Cash Dividends Declared Common Stock (per share)	(26,857)						(26,857)
Balance at End of Period at Sep. 30, 2020	1,361,739			$ 580	588,632	14,399	1,797,763		(1,039,635)
Ending Balance (in shares) at Sep. 30, 2020				40,060,675
Balance at Beginning of Period at Dec. 31, 2020	1,374,507			$ 580	591,360	7,822	1,811,979		(1,037,234)
Beginning Balance (in shares) at Dec. 31, 2020				40,119,312
Increase (decrease) in shareholders' equity
Net Income	59,949						59,949
Other Comprehensive Income (Loss)	(49,609)					(49,609)
Share-Based Compensation	2,780				2,780
Common Stock Issued under Purchase and Equity Compensation Plans	2,809				664		(845)		2,990
Common Stock Issued under Purchase and Equity Compensation Plans and Related Tax Benefits (in shares)				310,905
Common Stock Repurchased	(3,189)								(3,189)
Common Stock Repurchased (in shares)				(35,983)
Cash Dividends Declared Common Stock (per share)	(27,026)						(27,026)
Balance at End of Period at Mar. 31, 2021	1,360,221			$ 580	594,804	(41,787)	1,844,057		(1,037,433)
Ending Balance (in shares) at Mar. 31, 2021				40,394,234
Balance at Beginning of Period at Dec. 31, 2020	1,374,507			$ 580	591,360	7,822	1,811,979		(1,037,234)
Beginning Balance (in shares) at Dec. 31, 2020				40,119,312
Increase (decrease) in shareholders' equity
Net Income	189,535
Other Comprehensive Income (Loss)	(56,390)					(56,390)
Balance at End of Period at Sep. 30, 2021	1,597,109		$ 180,000	$ 580	598,341	(48,568)	1,916,861		(1,050,105)
Ending Balance (in shares) at Sep. 30, 2021			180,000	40,305,801
Balance at Beginning of Period at Mar. 31, 2021	1,360,221			$ 580	594,804	(41,787)	1,844,057		(1,037,433)
Beginning Balance (in shares) at Mar. 31, 2021				40,394,234
Increase (decrease) in shareholders' equity
Net Income	67,533						67,533
Other Comprehensive Income (Loss)	319					319
Share-Based Compensation	3,342				3,342
Preferred Stock Issued, Net	175,487		$ 180,000		(4,513)
Preferred Stock Issued, Net (in shares)			180,000
Common Stock Issued under Purchase and Equity Compensation Plans	3,851				628		(46)		3,269
Common Stock Issued under Purchase and Equity Compensation Plans and Related Tax Benefits (in shares)				72,421
Common Stock Repurchased	(109)								(109)
Common Stock Repurchased (in shares)				(1,173)
Cash Dividends Declared Common Stock (per share)	(27,113)						(27,113)
Balance at End of Period at Jun. 30, 2021	1,583,531		$ 180,000	$ 580	594,261	(41,468)	1,884,431		(1,034,273)
Ending Balance (in shares) at Jun. 30, 2021			180,000	40,465,482
Increase (decrease) in shareholders' equity
Net Income	62,053						62,053
Other Comprehensive Income (Loss)	(7,100)					(7,100)
Share-Based Compensation	3,536				3,536
Common Stock Issued under Purchase and Equity Compensation Plans	4,499				544		(327)		4,282
Common Stock Issued under Purchase and Equity Compensation Plans and Related Tax Benefits (in shares)				82,939
Common Stock Repurchased	(20,114)								(20,114)
Common Stock Repurchased (in shares)				(242,620)
Cash Dividends Declared Common Stock (per share)	(28,290)						(28,290)
Cash Dividends Declared Preferred Stock	(1,006)						(1,006)
Balance at End of Period at Sep. 30, 2021	$ 1,597,109		$ 180,000	$ 580	$ 598,341	$ (48,568)	$ 1,916,861		$ (1,050,105)
Ending Balance (in shares) at Sep. 30, 2021			180,000	40,305,801