Condensed Parent Company Financial Statements (Statements Of Cash Flows) (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
Operating Activities:
Net income	$ 101,204	$ 107,315	$ 21,659	$ 62,812	$ 85,964	$ 99,121	$ 81,466	$ 89,146	$ 292,990	$ 355,697	$ 343,166
Adjustments to reconcile net income to net cash provided by operating activities
Provision for credit losses									214,235	53,864
(Gains) losses on investment securities, net									2,373	(3,525)	2,000
Depreciation and amortization									96,369	88,362	67,665
Deferred income tax expense									(4,058)	44,557	55,224
Stock-based compensation expense									(4,938)	11,304	13,496
Decrease in other assets									(131,870)	(133,022)	(133,519)
Increase (decrease) in other liabilities									46,924	(11,898)	(27,001)
Net Cash (Used for) Provided by Operating Activities									(518,465)	265,993	377,182
Investing Activities:
Net cash paid for acquisitions, net									0	(108,365)	(53,871)
Net Cash Used for Investing Activities									(7,182,424)	(4,018,949)	(2,763,498)
Financing Activities:
(Decrease) increase in subordinated notes, other borrowings and junior subordinated debentures, net									88,596	15,480	137,257
Proceeds from the issuance of preferred stock, net									277,613	0	0
Issuance of common shares resulting from exercise of stock options, employee stock purchase plan and conversion of common stock warrants									15,059	10,667	15,903
Dividends paid									(85,890)	(65,110)	(50,987)
Common stock repurchases under authorized program									(92,055)	0	0
Common stock repurchases for tax withholdings related to stock-based compensation									(1,377)	(1,297)	(648)
Net Cash Provided by Financing Activities									7,736,887	3,647,232	2,500,925
Net Increase (Decrease) in Cash and Cash Equivalents									35,998	(105,724)	114,609
Cash and Cash Equivalents at Beginning of Period				286,476				392,200	286,476	392,200	277,591
Cash and Cash Equivalents at End of Period	322,474				286,476				322,474	286,476	392,200
Reportable Legal Entities | Parent Company
Operating Activities:
Net income									292,990	355,697	343,166
Adjustments to reconcile net income to net cash provided by operating activities
Provision for credit losses									0	(18)	56
(Gains) losses on investment securities, net									(192)	(1,900)	957
Depreciation and amortization									22,224	15,675	11,943
Deferred income tax expense									11,336	8,342	502
Stock-based compensation expense									(2,813)	5,611	6,025
Decrease in other assets									4,838	4,940	2,728
Increase (decrease) in other liabilities									2,388	(13,181)	650
Equity in undistributed net income of subsidiaries									(162,942)	(336,665)	(332,727)
Net Cash (Used for) Provided by Operating Activities									167,829	38,501	33,300
Investing Activities:
Capital (contributions to) distributions from subsidiaries, net									(12,000)	(22,500)	4,632
Net cash paid for acquisitions, net									0	(124,338)	(87,081)
Other investing activity, net									(40,127)	(51,495)	(57,143)
Net Cash Used for Investing Activities									(52,127)	(198,333)	(139,592)
Financing Activities:
(Decrease) increase in subordinated notes, other borrowings and junior subordinated debentures, net									(2,690)	273,886	101,910
Proceeds from the issuance of preferred stock, net									277,613	0	0
Issuance of common shares resulting from exercise of stock options, employee stock purchase plan and conversion of common stock warrants									15,059	10,667	15,903
Dividends paid									(85,890)	(65,110)	(50,987)
Common stock repurchases under authorized program									(92,055)	0	0
Common stock repurchases for tax withholdings related to stock-based compensation									(1,377)	(1,297)	(648)
Net Cash Provided by Financing Activities									110,660	218,146	66,178
Net Increase (Decrease) in Cash and Cash Equivalents									226,362	58,314	(40,114)
Cash and Cash Equivalents at Beginning of Period				$ 96,245				$ 37,931	96,245	37,931	78,045
Cash and Cash Equivalents at End of Period	$ 322,607				$ 96,245				$ 322,607	$ 96,245	$ 37,931