Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	[1]	Preferred Stock	Common Stock	Additional Paid-In Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	[1]	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning Balance at Dec. 31, 2019	$ 2,342,176	$ (43,807)		$ 0	$ 556,110	$ 1,499,681	$ 1,079,391	$ (43,807)		$ (137)	$ (792,869)
Beginning Balance (in shares) at Dec. 31, 2019				0	164,218
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	127,213						127,213
Other comprehensive income (loss)	57,091									57,091
Stock issued (in shares)					824
Common stock issued	5,046				$ 1,608	646					2,792
Stock-based compensation awards	5,403					5,403
Acquisition of treasury stock (in shares)					(2,908)
Acquisition of treasury stock	(39,748)										(39,748)
Common stock cash dividends	(63,109)						(63,109)
Ending Balance at Sep. 30, 2020	2,390,265			$ 0	$ 557,718	1,505,730	1,099,688			56,954	(829,825)
Ending Balance (in shares) at Sep. 30, 2020				0	162,134
Beginning Balance at Jun. 30, 2020	2,340,501			$ 0	$ 557,569	1,503,750	1,059,160			51,439	(831,417)
Beginning Balance (in shares) at Jun. 30, 2020				0	161,958
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	61,611						61,611
Other comprehensive income (loss)	5,515									5,515
Stock issued (in shares)					176
Common stock issued	1,846				$ 149	105					1,592
Stock-based compensation awards	1,875					1,875
Common stock cash dividends	(21,083)						(21,083)
Ending Balance at Sep. 30, 2020	2,390,265			$ 0	$ 557,718	1,505,730	1,099,688			56,954	(829,825)
Ending Balance (in shares) at Sep. 30, 2020				0	162,134
Beginning Balance at Dec. 31, 2020	2,616,828			$ 192,878	$ 557,917	1,508,117	1,120,781			65,091	(827,956)
Beginning Balance (in shares) at Dec. 31, 2020				200	162,350
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	213,611						213,611
Other comprehensive income (loss)	(39,476)									(39,476)
Stock issued (in shares)					770
Common stock issued	4,682				$ 1,705	2,309					668
Stock-based compensation awards	6,192					6,192
Preferred stock dividend	(7,715)						(7,715)
Acquisition of treasury stock (in shares)					(1,691)
Acquisition of treasury stock	(26,126)										(26,126)
Common stock cash dividends	(68,178)						(68,178)
Ending Balance at Sep. 30, 2021	2,699,818			$ 192,878	$ 559,622	1,516,618	1,258,499			25,615	(853,414)
Ending Balance (in shares) at Sep. 30, 2021				200	161,429
Beginning Balance at Jun. 30, 2021	2,692,958			$ 192,878	$ 559,485	1,513,645	1,208,086			47,201	(828,337)
Beginning Balance (in shares) at Jun. 30, 2021				200	162,988
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	75,583						75,583
Other comprehensive income (loss)	(21,586)									(21,586)
Stock issued (in shares)					132
Common stock issued	1,967				$ 137	781					1,049
Stock-based compensation awards	2,192					2,192
Preferred stock dividend	(2,562)						(2,562)
Acquisition of treasury stock (in shares)					(1,691)
Acquisition of treasury stock	(26,126)										(26,126)
Common stock cash dividends	(22,608)						(22,608)
Ending Balance at Sep. 30, 2021	$ 2,699,818			$ 192,878	$ 559,622	$ 1,516,618	$ 1,258,499			$ 25,615	$ (853,414)
Ending Balance (in shares) at Sep. 30, 2021				200	161,429

[1] The Corporation adopted ASU 2016-13 "Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses of Financial Instruments on January 1, 2020. See Note 1, "Basis of Presentation" to the Consolidated Financial Statements for further details.