Condensed Parent Company Financial Statements (Statements Of Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Expenses
Interest expense	$ 48,584	$ 55,220	$ 66,685	$ 82,624	$ 87,852	$ 89,775	$ 80,612	$ 71,984	$ 253,113	$ 330,223	$ 205,907
Salaries and employee benefits									626,076	546,420	480,077
Income (loss) before income taxes and equity in undistributed income of subsidiaries	134,711	137,284	30,703	87,083	116,682	134,601	110,173	118,645	389,781	480,101	460,133
Income tax benefit	(33,507)	(29,969)	(9,044)	(24,271)	(30,718)	(35,480)	(28,707)	(29,499)	(96,791)	(124,404)	(116,967)
Net income	$ 101,204	$ 107,315	$ 21,659	$ 62,812	$ 85,964	$ 99,121	$ 81,466	$ 89,146	292,990	355,697	343,166
Reportable Legal Entities | Parent Company
Income
Dividends and other revenue from subsidiaries									317,839	198,918	171,388
Investment securities (losses) gains and other income									(1,890)	3,044	4
Total income									315,949	201,962	171,392
Expenses
Interest expense									39,581	34,649	22,375
Salaries and employee benefits									75,179	72,925	64,726
Other expenses									113,886	116,132	108,038
Total expenses									228,646	223,706	195,139
Income (loss) before income taxes and equity in undistributed income of subsidiaries									87,303	(21,744)	(23,747)
Income tax benefit									42,745	40,776	34,186
Income before equity in undistributed net income of subsidiaries									130,048	19,032	10,439
Equity in undistributed net income of subsidiaries									162,942	336,665	332,727
Net income									$ 292,990	$ 355,697	$ 343,166