Condensed Parent Company Financial Statements (Statements Of Cash Flows) (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
Operating Activities:
Net income	$ 85,964	$ 99,121	$ 81,466	$ 89,146	$ 79,657	$ 91,948	$ 89,580	$ 81,981	$ 355,697	$ 343,166	$ 257,682
Adjustments to reconcile net income to net cash provided by operating activities
Provision for credit losses	7,826	$ 10,834	$ 24,580	10,624	10,401	$ 11,042	$ 5,043	8,346	53,864	34,832	29,768
Depreciation and amortization									88,362	67,665	63,107
Deferred income tax expense									44,557	55,224	63,243
Stock-based compensation expense									11,304	13,496	12,858
(Increase) decrease in other assets									(133,022)	(133,519)	(126,583)
(Decrease) increase in other liabilities									(11,898)	(27,001)	31,790
Net Cash Provided by Operating Activities									265,993	377,182	401,626
Investing Activities:
Net cash paid for acquisitions, net									(108,365)	(53,871)	(284)
Net Cash Used for Investing Activities									(4,018,949)	(2,763,498)	(2,303,232)
Financing Activities:
Increase in subordinated notes, other borrowings and junior subordinated debentures, net									15,480	137,257	(4,888)
Issuance of common shares resulting from exercise of stock options, employee stock purchase plan and conversion of common stock warrants									10,667	15,903	28,229
Dividends paid									(65,110)	(50,987)	(40,543)
Common stock repurchases for tax withholdings related to stock-based compensation									(1,297)	(648)	(397)
Net Cash Provided by Financing Activities									3,647,232	2,500,925	1,909,152
Net (Decrease) Increase in Cash and Cash Equivalents									(105,724)	114,609	7,546
Cash and Cash Equivalents at Beginning of Period				392,200				277,591	392,200	277,591	270,045
Cash and Cash Equivalents at End of Period	286,476				392,200				286,476	392,200	277,591
Reportable Legal Entities | Parent Company
Operating Activities:
Net income									355,697	343,166	257,682
Adjustments to reconcile net income to net cash provided by operating activities
Provision for credit losses									(18)	56	0
Depreciation and amortization									15,675	11,943	10,783
Deferred income tax expense									8,342	502	2,809
Stock-based compensation expense									5,611	6,025	5,185
(Increase) decrease in other assets									3,040	3,685	1,956
(Decrease) increase in other liabilities									(13,181)	650	9,967
Equity in undistributed net income of subsidiaries									(336,665)	(332,727)	(196,594)
Net Cash Provided by Operating Activities									38,501	33,300	91,788
Investing Activities:
Capital (contributions to) distributions from subsidiaries, net									(22,500)	4,632	(42,736)
Net cash paid for acquisitions, net									(124,338)	(87,081)	0
Other investing activity, net									(51,495)	(57,143)	(28,132)
Net Cash Used for Investing Activities									(198,333)	(139,592)	(70,868)
Financing Activities:
Increase in subordinated notes, other borrowings and junior subordinated debentures, net									273,886	101,910	20,008
Issuance of common shares resulting from exercise of stock options, employee stock purchase plan and conversion of common stock warrants									10,667	15,903	28,229
Dividends paid									(65,110)	(50,987)	(40,543)
Common stock repurchases for tax withholdings related to stock-based compensation									(1,297)	(648)	(397)
Net Cash Provided by Financing Activities									218,146	66,178	7,297
Net (Decrease) Increase in Cash and Cash Equivalents									58,314	(40,114)	28,217
Cash and Cash Equivalents at Beginning of Period				$ 37,931				$ 78,045	37,931	78,045	49,828
Cash and Cash Equivalents at End of Period	$ 96,245				$ 37,931				$ 96,245	$ 37,931	$ 78,045