Consolidated Statements Of Changes In Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock	Capital Surplus	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Non-Controlling Interest
Balance at Dec. 31, 2015	$ 2,367,418	$ 144,784	$ 489,862	$ 1,337,677	$ 383,313	$ (26,116)	$ 32,470	$ 5,428
Net income	276,854				275,391			1,463
Other comprehensive income	(21,495)						(21,495)
Distributions to non-controlling interest	(1,542)							(1,542)
Purchase of treasury stock	(39,381)					(39,381)
Cash dividends paid on common stock	(87,070)				(87,070)
Cash dividends paid on preferred stock	(9,000)				(9,000)
Excess tax benefit related to equity compensation plans	3,390			3,390
Stock-based compensation	11,525			11,525
Issuance under stock purchase and equity compensation plans, net	911			(15,810)		16,721
5% stock dividend, net	(478)		20,153	215,672	(269,785)	33,482
Balance at Dec. 31, 2016	2,501,132	144,784	510,015	1,552,454	292,849	(15,294)	10,975	5,349
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-09 [Member]	1,297			3,441	(2,144)
Net income	319,900				319,383			517
Other comprehensive income	3,133						3,133
Distributions to non-controlling interest	(1,293)							(1,293)
Sale of non-controlling interest in subsidiary	1			2,950				(2,949)
Purchase of treasury stock	(17,771)					(17,771)
Cash dividends paid on common stock	(91,619)				(91,619)
Cash dividends paid on preferred stock	(9,000)				(9,000)
Stock-based compensation	12,105			12,105
Issuance under stock purchase and equity compensation plans, net	858			(17,734)		18,592
5% stock dividend, net	(559)		25,392	262,144	(288,095)
Balance at Dec. 31, 2017	2,718,184	144,784	535,407	1,815,360	221,374	(14,473)	14,108	1,624
Cumulative Effect of New Accounting Principle in Period of Adoption
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2018-02 [Member]	0				(2,932)		2,932
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-01 [Member]	0				33,320		(33,320)
Net income	438,214				433,542			4,672
Other comprehensive income	(48,389)						(48,389)
Distributions to non-controlling interest	(445)							(445)
Purchase of treasury stock	(75,231)					(75,231)
Cash dividends paid on common stock	(100,238)				(100,238)
Cash dividends paid on preferred stock	(9,000)				(9,000)
Stock-based compensation	12,841			12,841
Issuance under stock purchase and equity compensation plans, net	1,792			(21,632)		23,424
5% stock dividend, net	(579)		24,025	278,255	(334,903)	32,044
Balance at Dec. 31, 2018	$ 2,937,149	$ 144,784	$ 559,432	$ 2,084,824	$ 241,163	$ (34,236)	$ (64,669)	$ 5,851