CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Series A Preferred Stock	Series B Preferred Stock	Preferred Stock	Common Stock	Common Stock Common Stock	Surplus	Surplus Common Stock	Retained Earnings	Retained Earnings Common Stock	Retained Earnings Series A Preferred Stock	Retained Earnings Series B Preferred Stock	Accumulated Other Comprehensive Loss	Treasury Stock	Treasury Stock Common Stock
Beginning balance at Dec. 31, 2016	$ 2,377,156				$ 111,590	$ 92,353		$ 2,044,401		$ 172,754				$ (42,093)	$ (1,849)
Beginning balance (in shares) at Dec. 31, 2016						263,639
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Reclassification due to the adoption of ASU No. 2018-02										7,927				(7,927)
Net income	161,907									161,907
Other comprehensive income (loss), net of tax	4,015													4,015
Cash dividends declared on preferred stock			$ (7,188)	$ (2,261)								$ (7,188)	$ (2,261)
Cash dividends declared on common stock		$ (116,332)									$ (116,332)
Effect of stock incentive plan, net (in shares)						117
Effect of stock incentive plan, net	9,560					$ 229		11,297		(18)					(1,948)
Stock issued (in shares)							713
Stock issued		8,207			98,101		$ 145		$ 4,658		(56)				3,460
Ending balance at Dec. 31, 2017	2,533,165				209,691	$ 92,727		2,060,356		216,733				(46,005)	(337)
Ending balance (in shares) at Dec. 31, 2017						264,469
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	261,428									261,428
Other comprehensive income (loss), net of tax	(22,885)													(22,885)
Cash dividends declared on preferred stock			(7,188)	(5,500)								(7,188)	(5,500)
Cash dividends declared on common stock		(146,346)									(146,346)
Effect of stock incentive plan, net (in shares)						1,955
Effect of stock incentive plan, net	17,180					$ 771		21,022		(2,415)					(2,198)
Stock issued (in shares)							65,007
Stock issued		738,211					$ 22,742		715,121							$ 348
Ending balance at Dec. 31, 2018	3,350,454				209,691	$ 116,240		2,796,499		299,642				(69,431)	(2,187)
Ending balance (in shares) at Dec. 31, 2018						331,431
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	309,793									309,793
Other comprehensive income (loss), net of tax	37,217													37,217
Cash dividends declared on preferred stock			$ (7,188)	$ (5,500)								$ (7,188)	$ (5,500)
Cash dividends declared on common stock		(154,689)									$ (154,689)
Effect of stock incentive plan, net (in shares)						726
Effect of stock incentive plan, net	15,878					$ 291		15,346		(1,467)					1,708
Stock issued (in shares)							71,121
Stock issued		$ 835,255					$ 24,892		$ 810,363
Ending balance at Dec. 31, 2019	$ 4,384,188				$ 209,691	$ 141,423		$ 3,622,208		$ 443,559				$ (32,214)	$ (479)
Ending balance (in shares) at Dec. 31, 2019						403,278