Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
OPERATING ACTIVITIES
Net income	$ 323,752	$ 225,482	$ 210,386
Adjustments to reconcile net income to cash provided by operating activities:
Provision for loan and lease losses	25,692	32,941	20,664
Deferred tax expense (benefit)	125,838	33,146	550
Change in current taxes payable	(10,616)	(24,380)	(19,477)
Depreciation	90,804	88,777	87,717
Change in accrued interest payable	155	(1,916)	(2,481)
Change in income earned not collected	(8,899)	(7,805)	(12,782)
Gain on acquisitions	(134,745)	(5,831)	(42,930)
Gain (Loss) on Disposition of Business	0	0	(216)
Securities losses (gains)	(4,293)	(26,673)	(10,817)
Gain (Loss) on Contract Termination	45	3,377	0
Origination of loans held for sale	(622,503)	(795,963)	(685,631)
Proceeds from sale of loans held for sale	660,808	797,123	701,412
Gain on sale of loans	(14,843)	(15,795)	(11,851)
Gain (Loss) on Sale of Loans and Leases	(1,007)	(3,758)	0
Loss on sale of other real estate	4,460	6,201	2,168
Gain (Loss) on Disposition of Property Plant Equipment	(524)	0	0
Gain (Loss) on Extinguishment of Debt	919	1,717	0
Net amortization of premiums and discounts	(40,028)	(44,618)	(85,066)
Amortization of intangible assets	22,842	21,808	22,894
FDIC receivable for loss share agreements	7,764	14,745	47,044
FDIC payable for loss share agreements	4,334	(11,245)	9,918
Net change in other assets	(46,920)	(27,873)	(12,904)
Net change in other liabilities	(29,542)	(25,520)	14,458
Net cash provided by operating activities	351,655	230,506	233,056
INVESTING ACTIVITIES
Net change in loans outstanding	(1,213,686)	(1,214,433)	(1,311,447)
Purchases of investment securities available for sale	(3,648,312)	(4,086,855)	(2,467,993)
Proceeds from maturities of investment securities held to maturity	22	157	263
Proceeds from maturities of investment securities available for sale	1,842,563	2,149,130	1,478,608
Proceeds from sales of investment securities available for sale	1,345,746	1,829,305	1,286,120
Net change in overnight investments	586,279	233,433	(338,213)
Cash (paid to) received from the FDIC for loss share agreements	(7,440)	(21,059)	(33,296)
Net Payment to the FDIC for Termination of Loss Share Agreements	(285)	(20,115)	0
Proceeds from Sale of Other Real Estate	40,709	34,944	80,932
Proceeds from Sale of Property, Plant, and Equipment	3,061	0	0
Proceeds from sale of portfolio loans	162,649	77,665	45,862
Additions to premises and equipment	(84,798)	(81,841)	(89,734)
Net Cash Used in Divestiture of Businesses	0	0	(22,242)
Business acquisitions, net of cash acquired	304,820	(727)	123,137
Net cash (used) provided by investing activities	(668,672)	(1,100,396)	(1,248,003)
FINANCING ACTIVITIES
Net change in time deposits	(538,250)	(505,548)	(590,773)
Net change in demand and other interest-bearing deposits	539,120	1,287,856	1,607,487
Net change in short-term borrowings	(44,680)	(33,072)	(397,952)
Repayment of long-term obligations	(6,955)	(9,279)	(5,896)
Origination of long-term obligations	175,000	150,000	350,000
Cash dividends paid	(10,809)	(14,412)	(18,015)
Net cash provided (used) by financing activities	113,426	875,545	944,851
Change in cash and due from banks	(203,591)	5,655	(70,096)
Cash and due from banks at beginning of period	539,741	534,086	604,182
Cash and due from banks at end of period	336,150	539,741	534,086
CASH PAYMENTS FOR:
Interest	43,639	44,998	46,785
Income taxes	88,565	108,741	136,900
SUPPLEMENTAL DISCLOSURE OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Transfers of loans to other real estate	34,980	35,272	55,032
Dividends declared but not paid	4,204	0	0
Unsettled sales of investment securities	309,623	0	0
Reclassification of portfolio loans to loans held for sale	$ 161,719	$ 73,907	$ 0