Condensed Parent Company Financial Statements (Statements Of Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Expenses
Interest expense	$ 87,852	$ 89,775	$ 80,612	$ 71,984	$ 66,508	$ 57,399	$ 45,877	$ 36,123	$ 330,223	$ 205,907	$ 114,392
Salaries and employee benefits									546,420	480,077	430,078
(Loss) income before income taxes and equity in undistributed income of subsidiaries	116,682	134,601	110,173	118,645	107,662	122,814	121,591	108,066	480,101	460,133	389,997
Income tax benefit	(30,718)	(35,480)	(28,707)	(29,499)	(28,005)	(30,866)	(32,011)	(26,085)	(124,404)	(116,967)	(132,315)
Net income	$ 85,964	$ 99,121	$ 81,466	$ 89,146	$ 79,657	$ 91,948	$ 89,580	$ 81,981	355,697	343,166	257,682
Reportable Legal Entities | Parent Company
Income
Dividends and other revenue from subsidiaries									198,918	171,388	155,969
Other income									3,044	4	2,488
Total income									201,962	171,392	158,457
Expenses
Interest expense									34,649	22,375	19,207
Salaries and employee benefits									72,925	64,726	50,683
Other expenses									116,132	108,038	74,618
Total expenses									223,706	195,139	144,508
(Loss) income before income taxes and equity in undistributed income of subsidiaries									(21,744)	(23,747)	13,949
Income tax benefit									40,776	34,186	47,139
Income before equity in undistributed net income of subsidiaries									19,032	10,439	61,088
Equity in undistributed net income of subsidiaries									336,665	332,727	196,594
Net income									$ 355,697	$ 343,166	$ 257,682