Condensed Parent Company Financial Statements (Statements Of Cash Flows) (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Jun. 30, 2016	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Activities:
Net income		$ 79,657	$ 91,948	$ 89,580	$ 81,981	$ 68,781	$ 65,626	$ 64,897	$ 58,378	$ 343,166	$ 257,682	$ 206,875
Adjustments to reconcile net income to net cash provided by (used for) operating activities
Provision for credit losses		10,401	$ 11,042	$ 5,043	8,346	7,772	$ 7,896	$ 8,891	5,209	34,832	29,768	34,084
Gain on early extinguishment of debt										0	0	(3,588)
Depreciation and amortization										67,665	63,107	53,148
Deferred income tax expense (benefit)										55,224	63,243	6,676
Stock-based compensation expense										13,496	12,858	9,303
Decrease (increase) in other assets										(133,519)	(126,583)	(43,953)
Increase in other liabilities										(27,001)	31,790	114,531
Net Cash Provided by Operating Activities										377,182	401,626	310,966
Investing Activities:
Net cash paid for acquisitions, net										(53,871)	(284)	(613,619)
Net Cash Used for Investing Activities										(2,763,498)	(2,303,232)	(2,492,326)
Financing Activities:
Increase (decrease) in subordinated notes, other borrowings and junior subordinated debentures, net										137,257	(4,888)	(3,405)
Proceeds from the issuance of common stock, net	$ 152,900									0	0	152,911
Issuance of common shares resulting from exercise of stock options, employee stock purchase plan and conversion of common stock warrants										15,903	28,229	15,828
Dividends paid										(50,987)	(40,543)	(38,568)
Common stock repurchases for tax withholdings related to stock-based compensation										(648)	(397)	(616)
Net Cash Provided by Financing Activities										2,500,925	1,909,152	2,175,610
Net Increase (Decrease) in Cash and Cash Equivalents										114,609	7,546	(5,750)
Cash and Cash Equivalents at Beginning of Period					277,591				270,045	277,591	270,045	275,795
Cash and Cash Equivalents at End of Period		392,200				277,591				392,200	277,591	270,045
Reportable Legal Entities | Parent Company
Operating Activities:
Net income										343,166	257,682	206,875
Adjustments to reconcile net income to net cash provided by (used for) operating activities
Provision for credit losses										56	0	0
Gain on early extinguishment of debt										0	0	(4,305)
Depreciation and amortization										11,943	10,783	10,400
Deferred income tax expense (benefit)										502	2,809	(601)
Stock-based compensation expense										6,025	5,185	3,762
Decrease (increase) in other assets										3,685	1,956	(319)
Increase in other liabilities										650	9,967	9,618
Equity in undistributed net income of subsidiaries										(332,727)	(196,594)	(197,861)
Net Cash Provided by Operating Activities										33,300	91,788	27,569
Investing Activities:
Capital distributions from (contributions to) subsidiaries, net										4,632	(42,736)	(118,575)
Net cash paid for acquisitions, net										(87,081)	0	(61,308)
Other investing activity, net										(57,143)	(28,132)	(18,051)
Net Cash Used for Investing Activities										(139,592)	(70,868)	(197,934)
Financing Activities:
Increase (decrease) in subordinated notes, other borrowings and junior subordinated debentures, net										101,910	20,008	(26,251)
Proceeds from the issuance of common stock, net										0	0	152,911
Issuance of common shares resulting from exercise of stock options, employee stock purchase plan and conversion of common stock warrants										15,903	28,229	15,828
Dividends paid										(50,987)	(40,543)	(38,568)
Common stock repurchases for tax withholdings related to stock-based compensation										(648)	(397)	(616)
Net Cash Provided by Financing Activities										66,178	7,297	103,304
Net Increase (Decrease) in Cash and Cash Equivalents										(40,114)	28,217	(67,061)
Cash and Cash Equivalents at Beginning of Period					$ 78,045				$ 49,828	78,045	49,828	116,889
Cash and Cash Equivalents at End of Period		$ 37,931				$ 78,045				$ 37,931	$ 78,045	$ 49,828