Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
OPERATING ACTIVITIES
Net income	$ 225,482	$ 210,386	$ 138,562
Adjustments to reconcile net income to cash provided by operating activities:
Provision for loan and lease losses	32,941	20,664	640
Deferred tax expense (benefit)	33,146	550	(33,339)
Change in current taxes payable	(24,380)	(19,477)	72,274
Depreciation	88,777	87,717	75,481
Change in accrued interest payable	(1,916)	(2,481)	1,457
Change in income earned not collected	(7,805)	(12,782)	6,402
Gain on acquisitions	(5,831)	(42,930)	0
Gain (Loss) on Disposition of Business	0	(216)	0
Securities losses (gains)	(26,673)	(10,817)	(29,096)
Gain (Loss) on Contract Termination	3,377	0	0
Origination of loans held for sale	(795,963)	(685,631)	(377,993)
Proceeds from sale of loans held for sale	797,123	701,412	398,719
Gain on sale of loans	(15,795)	(11,851)	(4,971)
Gain (Loss) on Sale of Loans and Leases	(3,758)	0	0
Loss on sale of other real estate	6,201	2,168	14,275
Gain on elimination of acquired debt	0	0	(1,988)
Net amortization of premiums and discounts	(44,618)	(85,066)	(48,374)
Amortization of intangible assets	21,808	22,894	6,955
FDIC receivable for loss share agreements	14,745	47,044	27,666
FDIC payable for loss share agreements	(11,245)	9,918	6,933
Net change in other assets	(27,656)	(12,904)	(72,680)
Net change in other liabilities	(25,520)	14,458	1,319
Net cash provided by operating activities	232,440	233,056	182,242
INVESTING ACTIVITIES
Net change in loans outstanding	(1,214,433)	(1,311,447)	(814,372)
Purchases of investment securities available for sale	(4,086,855)	(2,467,993)	(2,518,680)
Proceeds from maturities of investment securities held to maturity	157	263	389
Proceeds from maturities of investment securities available for sale	2,149,130	1,478,608	2,482,722
Proceeds from sales of investment securities available for sale	1,829,305	1,286,120	422,652
Net change in overnight investments	233,433	(338,213)	221,730
Cash (paid to) received from the FDIC for loss share agreements	(21,059)	(33,296)	(1,286)
Net Payment to the FDIC for Termination of Loss Share Agreements	(20,115)	0	0
Proceeds from Sale of Other Real Estate	34,944	80,932	89,485
Proceeds from Sale of Loans Held-for-investment	77,665	45,862	0
Additions to premises and equipment	(81,841)	(89,734)	(82,708)
Net Cash Used in Divestiture of Businesses	0	(22,242)	0
Business acquisitions, net of cash acquired	(727)	123,137	182,370
Net cash (used) provided by investing activities	(1,100,396)	(1,248,003)	(17,698)
FINANCING ACTIVITIES
Net change in time deposits	(505,548)	(590,773)	(499,869)
Net change in demand and other interest-bearing deposits	1,287,856	1,607,487	497,692
Net change in short-term borrowings	(33,072)	(397,952)	(25,321)
Repayment of long-term obligations	(11,213)	(5,896)	(54,301)
Origination of long-term obligations	150,000	350,000	0
Stock issuance costs	0	0	(619)
Cash dividends paid	(14,412)	(18,015)	(11,543)
Net cash provided (used) by financing activities	873,611	944,851	(93,961)
Change in cash and due from banks	5,655	(70,096)	70,583
Cash and due from banks at beginning of period	534,086	604,182	533,599
Cash and due from banks at end of period	539,741	534,086	604,182
CASH PAYMENTS FOR:
Interest	44,998	46,785	48,894
Income taxes	108,741	136,900	127,970
SUPPLEMENTAL DISCLOSURE OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Transfers of loans to other real estate	35,272	55,032	65,956
Dividends declared but not paid	0	0	3,603
Repurchase and retirement of common stock	0	0	(46,085)
Issuance of common stock associated with Bancorporation merger	$ 0	$ 0	$ 564,248