CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjusted Balance	Common Stock	Series A Preferred Stock	Series B Preferred Stock	Preferred Stock	Preferred Stock Cumulative Effect, Period of Adoption, Adjusted Balance	Common Stock	Common Stock Cumulative Effect, Period of Adoption, Adjusted Balance	Common Stock Common Stock	Surplus	Surplus Cumulative Effect, Period of Adoption, Adjusted Balance	Surplus Common Stock	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings Cumulative Effect, Period of Adoption, Adjusted Balance	Retained Earnings Common Stock	Retained Earnings Series A Preferred Stock	Retained Earnings Series B Preferred Stock	Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Loss Cumulative Effect, Period of Adoption, Adjusted Balance	Treasury Stock	Treasury Stock Cumulative Effect, Period of Adoption, Adjusted Balance	Treasury Stock Common Stock
Beginning balance at Dec. 31, 2017	$ 2,533,165		$ 2,515,554				$ 209,691	$ 209,691	$ 92,727	$ 92,727		$ 2,060,356	$ 2,060,356		$ 216,733		$ 199,663				$ (46,005)		$ (46,546)	$ (337)	$ (337)
Beginning balance (ASU 2016-01) at Dec. 31, 2017																$ 480						$ (480)
Beginning balance (ASU 2017-12) at Dec. 31, 2017																61						$ (61)
Beginning balance (ASU 2016-16) at Dec. 31, 2017		$ (17,611)														(17,611)
Beginning balance (in shares) at Dec. 31, 2017									264,469	264,469
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	261,428														261,428
Other comprehensive 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)
Common stock issued (in shares)											65,007
Common stock issued				738,211							$ 22,742			$ 715,121												$ 348
Ending balance at Dec. 31, 2018	$ 3,350,454		3,353,422				209,691	209,691	$ 116,240	$ 116,240		2,796,499	2,796,499		299,642		302,610				(69,431)		(69,431)	(2,187)	(2,187)
Ending balance (ASU 2016-02) at Dec. 31, 2018		4,414														4,414
Ending balance (ASU 2017-08) at Dec. 31, 2018		(1,446)														(1,446)
Ending balance (in shares) at Dec. 31, 2018									331,431	331,431
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Net income	$ 309,793														309,793
Other comprehensive 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
Common stock issued (in shares)											71,121
Common stock issued				835,255							$ 24,892			$ 810,363
Ending balance at Dec. 31, 2019	4,384,188	$ (28,187)	$ 4,356,001				209,691	$ 209,691	$ 141,423	$ 141,423		3,622,208	$ 3,622,208		443,559	$ (28,187)	$ 415,372				(32,214)		$ (32,214)	(479)	$ (479)
Ending balance (in shares) at Dec. 31, 2019									403,278	403,278
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	390,606														390,606
Other comprehensive loss,  net of tax	24,496																				24,496
Cash dividends declared on preferred stock					$ (7,188)	$ (5,500)													$ (7,188)	$ (5,500)
Cash dividends declared on common stock				$ (179,277)														$ (179,277)
Effect of stock incentive plan, net (in shares)									581
Effect of stock incentive plan, net	12,982								$ 323			15,260			(2,855)									254
Ending balance at Dec. 31, 2020	$ 4,592,120						$ 209,691		$ 141,746			$ 3,637,468			$ 611,158						$ (7,718)			$ (225)
Ending balance (in shares) at Dec. 31, 2020									403,859