Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
OPERATING ACTIVITIES
Net income	$ 400,313	$ 323,752	$ 225,482
Adjustments to reconcile net income to cash provided by operating activities:
Provision for loan and lease losses	28,468	25,692	32,941
Deferred tax expense (benefit)	(13,377)	125,838	33,146
Change in current taxes payable	23,353	(10,616)	(24,380)
Depreciation	96,781	90,804	88,777
Change in accrued interest payable	(240)	155	(1,916)
Change in income earned not collected	(10,785)	(8,899)	(7,805)
Gain on acquisitions	0	(134,745)	(5,831)
Securities losses (gains)	(351)	(4,293)	(26,673)
Marketable equity securities losses, net	7,610	0	0
Gain (Loss) on Contract Termination	0	45	3,377
Origination of loans held for sale	(593,307)	(622,503)	(795,963)
Proceeds from sale of loans held for sale	608,549	660,808	797,123
Gain on sale of loans	(11,210)	(14,843)	(15,795)
Gain (Loss) on Sale of Loans and Leases	0	(1,007)	(3,758)
Loss on sale of other real estate	4,390	4,460	6,201
Gain (Loss) on Disposition of Property Plant Equipment	2,452	(524)	0
Gain on extinguishment of debt	(26,553)	(919)	(1,717)
Net amortization of premiums and discounts	(36,567)	(40,028)	(44,618)
Amortization of intangible assets	23,648	22,842	21,808
FDIC payable for loss share agreements	4,276	4,334	(11,245)
Originations of mortgage servicing rights	(5,258)	(7,178)	(5,931)
Net change in other assets	304,503	(31,978)	(7,197)
Net change in other liabilities	(40,895)	(25,939)	(25,520)
Net cash provided by operating activities	765,800	355,258	230,506
INVESTING ACTIVITIES
Net change in loans outstanding	(1,023,885)	(1,213,686)	(1,214,433)
Purchases of investment securities available for sale	(1,451,287)	(3,648,312)	(4,086,855)
Purchases of investment securities held to maturity	(97,827)	0	0
Purchases of marketable equity securities	(2,818)	0	0
Proceeds from maturities of investment securities held to maturity	296,632	22	157
Proceeds from maturities of investment securities available for sale	1,564,730	1,842,563	2,149,130
Proceeds from sales of investment securities available for sale	151,754	1,345,746	1,829,305
Proceeds from sales of marketable equity securities	9,528	0	0
Net change in overnight investments	601,979	586,279	233,433
Cash (paid to) received from the FDIC for loss share agreements	(3,567)	(7,440)	(21,059)
Net Payment to the FDIC for Termination of Loss Share Agreements	0	(285)	(20,115)
Proceeds from Sale of Other Real Estate	28,128	40,709	34,944
Proceeds from Sale of Property, Plant, and Equipment	1,721	3,061	0
Proceeds from sale of portfolio loans	9,591	162,649	77,665
Additions to premises and equipment	(140,444)	(84,798)	(81,841)
Business acquisitions, net of cash acquired	(155,126)	304,820	(727)
Net cash (used) provided by investing activities	(210,891)	(668,672)	(1,100,396)
FINANCING ACTIVITIES
Net change in time deposits	33,023	(538,250)	(505,548)
Net change in demand and other interest-bearing deposits	457,196	539,120	1,287,856
Net decrease in short-term borrowings	(246,517)	(44,680)	(33,072)
Repayment of long-term obligations	(752,447)	(6,955)	(9,279)
Origination of long-term obligations	125,000	175,000	150,000
Repurchase of common stock	(163,095)	0	0
Cash dividends paid	(16,779)	(14,412)	(14,412)
Net cash provided (used) by financing activities	(563,619)	109,823	875,545
Change in cash and due from banks	(8,710)	(203,591)	5,655
Cash and due from banks at beginning of period	336,150	539,741	534,086
Cash and due from banks at end of period	327,440	336,150	539,741
CASH PAYMENTS FOR:
Interest	37,097	43,639	44,998
Income taxes	73,806	88,565	108,741
SUPPLEMENTAL DISCLOSURE OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Transfers of loans to other real estate	23,375	34,980	35,272
Dividends declared but not paid	4,668	4,204	0
Reclassification of portfolio loans (from) to loans held for sale	(2,433)	161,719	73,907
Transfer of investment securities available for sale to held to maturity	2,485,761	0	0
Transfer of investment securities available for sale to marketable equity securities	107,578	0	0
Premises and equipment acquired through capital leases and other financing arrangements	12,196	5,327	0
Transfers of premises and equipment to other real estate	1,622	0	0
Unsettled sales of investment securities	0	309,623	0
Unsettled common stock repurchases	$ (2,243)	$ 0	$ 0