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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities:
Net income		$ 68,781	$ 65,626	$ 64,897	$ 58,378	$ 54,608	$ 53,115	$ 50,041	$ 49,111	$ 257,682	$ 206,875	$ 156,749
Adjustments to reconcile net income to net cash provided by (used for) operating activities
Provision for credit losses		7,772	$ 7,896	$ 8,891	5,209	7,350	$ 9,571	$ 9,129	8,034	29,768	34,084	32,942
Gain on early extinguishment of debt										0	(3,588)	0
Depreciation and amortization										63,107	53,148	41,010
Deferred income tax expense (benefit)										63,243	6,676	23,054
Stock-based compensation expense										12,858	9,303	9,656
(Decrease) increase in other assets										(126,071)	(43,614)	(151,132)
Increase in other liabilities										30,693	113,258	292
Net Cash Provided by Operating Activities										401,041	310,032	38,966
Investing Activities:
Net cash paid for acquisitions, net										(284)	(613,619)	(15,428)
Net Cash Used for Investing Activities										(2,303,744)	(2,492,665)	(1,641,553)
Financing Activities:
Increase (decrease) in subordinated notes, other borrowings and junior subordinated debentures, net										(4,888)	(3,405)	44,415
Proceeds from the issuance of common stock, net	$ 152,900									0	152,911	0
Net proceeds from issuance of Series D Preferred Stock										0	0	120,842
Issuance of common shares resulting from exercise of stock options, employee stock purchase plan and conversion of common stock warrants										28,229	15,828	16,119
Dividends paid										(40,543)	(38,568)	(29,888)
Common stock repurchases for tax withholdings related to stock-based compensation										(397)	(616)	(424)
Net Cash Provided by Financing Activities										1,910,249	2,176,883	1,647,675
Net Increase (Decrease) in Cash and Cash Equivalents										7,546	(5,750)	45,088
Cash and Cash Equivalents at Beginning of Period					270,045				275,795	270,045	275,795	230,707
Cash and Cash Equivalents at End of Period		277,591				270,045				277,591	270,045	275,795
Reportable Legal Entities | Parent Company
Operating Activities:
Net income										257,682	206,875	156,749
Adjustments to reconcile net income to net cash provided by (used for) operating activities
Provision for credit losses										0	0	(96)
Gain on early extinguishment of debt										0	(4,305)	0
Depreciation and amortization										10,783	10,400	8,323
Deferred income tax expense (benefit)										2,809	(601)	(1,872)
Stock-based compensation expense										5,185	3,762	3,354
(Decrease) increase in other assets										1,956	(319)	(39,051)
Increase in other liabilities										9,967	9,618	21,840
Equity in undistributed net income of subsidiaries										(196,594)	(197,861)	(183,830)
Net Cash Provided by Operating Activities										91,788	27,569	(34,583)
Investing Activities:
Capital contributions to subsidiaries, net										(42,736)	(118,575)	(97,400)
Net cash paid for acquisitions, net										0	(61,308)	(51,060)
Other investing activity, net										(28,132)	(18,051)	(24,908)
Net Cash Used for Investing Activities										(70,868)	(197,934)	(173,368)
Financing Activities:
Increase (decrease) in subordinated notes, other borrowings and junior subordinated debentures, net										20,008	(26,251)	66,888
Proceeds from the issuance of common stock, net										0	152,911	0
Net proceeds from issuance of Series D Preferred Stock										0	0	120,842
Issuance of common shares resulting from exercise of stock options, employee stock purchase plan and conversion of common stock warrants										28,229	15,828	16,119
Dividends paid										(40,543)	(38,568)	(29,888)
Common stock repurchases for tax withholdings related to stock-based compensation										(397)	(616)	(424)
Net Cash Provided by Financing Activities										7,297	103,304	173,537
Net Increase (Decrease) in Cash and Cash Equivalents										28,217	(67,061)	(34,414)
Cash and Cash Equivalents at Beginning of Period					$ 49,828				$ 116,889	49,828	116,889	151,303
Cash and Cash Equivalents at End of Period		$ 78,045				$ 49,828				$ 78,045	$ 49,828	$ 116,889