Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	[2]	Preferred Stock Issuance	Common Stock Issuance	Preferred Stock	Preferred Stock Preferred Stock Issuance	Common Stock	Common Stock Common Stock Issuance	Additional Paid-in Capital	Additional Paid-in Capital Common Stock Issuance	Retained Earnings		Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	[2]	Accumulated Other Comprehensive (Loss) Income		Treasury Stock	Treasury Stock Common Stock Issuance
Beginning Balance at Dec. 31, 2017	$ 2,229,857					$ 0		$ 552,232		$ 1,478,389		$ 821,619				$ (32,974)		$ (589,409)
Beginning Balance (in shares) at Dec. 31, 2017						0		175,170
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	208,393											208,393
Other comprehensive income (loss)	(18,988)															(18,988)
Stock issued	6,735							$ 2,062		3,432								1,241
Stock issued (in shares)								977
Stock-based compensation awards	7,965							$ 83		7,882
Stock-based compensation awards (in shares)								33
Acquisition of treasury stock	(95,308)																	(95,308)
Acquisition of treasury stock (in shares)								(5,996)
Reclassification of stranded tax effects	0											7,101	[1]			(7,101)	[1]
Common stock cash dividends	(91,081)											(91,081)
Ending Balance at Dec. 31, 2018	2,247,573					$ 0		$ 554,377		1,489,703		946,032				(59,063)		(683,476)
Ending Balance (in shares) at Dec. 31, 2018						0		170,184
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	226,339											226,339
Other comprehensive income (loss)	58,926															58,926
Stock issued	6,362							$ 1,733		2,565								2,064
Stock issued (in shares)								883
Stock-based compensation awards	7,413									7,413
Acquisition of treasury stock	(111,457)																	(111,457)
Acquisition of treasury stock (in shares)								(6,849)
Common stock cash dividends	(92,980)											(92,980)
Ending Balance at Dec. 31, 2019	2,342,176					$ 0		$ 556,110		1,499,681		1,079,391				(137)		(792,869)
Ending Balance (in shares) at Dec. 31, 2019						0		164,218
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	178,040											178,040
Other comprehensive income (loss)	65,228															65,228
Stock issued				$ 192,878	$ 7,375		$ 192,878		$ 1,807		$ 907								$ 4,661
Stock issued (in shares)							200		1,040
Stock-based compensation awards	7,529									7,529
Acquisition of treasury stock	(39,748)																	(39,748)
Acquisition of treasury stock (in shares)								(2,908)
Common stock cash dividends	(90,708)											(90,708)
Preferred stock dividend	(2,135)											(2,135)
Ending Balance at Dec. 31, 2020	$ 2,616,828	$ (43,807)				$ 192,878		$ 557,917		$ 1,508,117		$ 1,120,781		$ (43,807)		$ 65,091		$ (827,956)
Ending Balance (in shares) at Dec. 31, 2020						200		162,350

[1] Result of adoption of ASU 2018-02. See Note 1 to Consolidated Financial Statements for further details.

[2] 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 to the Consolidated Financial Statements for further details.