Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
OPERATING ACTIVITIES
Net income	$ 457,371	$ 400,313	$ 323,752
Adjustments to reconcile net income to cash provided by operating activities:
Provision for loan and lease losses	31,441	28,468	25,692
Deferred tax expense (benefit)	54,598	(13,377)	125,838
Change in current taxes payable	(19,564)	23,353	(10,616)
Depreciation	103,828	96,781	90,804
Change in accrued interest payable	14,412	(240)	155
Change in income earned not collected	(4,151)	(10,785)	(8,899)
Gain on acquisitions	0	0	(134,745)
Realized gains on investment securities available for sale, net	(7,115)	(351)	(4,293)
Marketable equity securities (gains) losses, net	(20,625)	7,610	0
Gain on extinguishment of debt	0	(26,553)	(919)
Origination of loans held for sale	(736,015)	(593,307)	(622,503)
Proceeds from sale of loans held for sale	731,803	608,549	660,808
Gain on sale of loans	(14,884)	(11,210)	(14,843)
Gain (Loss) on Sale of Loans and Leases	(299)	0	(1,007)
Loss on sale of other real estate	2,664	4,390	4,460
Gain (Loss) on Disposition of Property Plant Equipment	4,115	2,452	(524)
Net amortization of premiums and discounts	(34,040)	(36,567)	(40,028)
Amortization of intangible assets	23,861	23,648	22,842
FDIC payable for loss share agreements	6,777	4,276	4,334
Net change in other liabilities	(5,927)	(5,258)	(7,178)
Net change in other assets	(28,097)	(3,961)	(31,933)
Net change in other liabilities	(19,584)	(40,895)	(25,939)
Net cash provided by operating activities	540,569	457,336	355,258
INVESTING ACTIVITIES
Net change in loans outstanding	(1,282,880)	(1,023,885)	(1,213,686)
Payments to Acquire Available-for-sale Securities	(4,705,038)	(1,451,287)	(3,648,312)
Purchases of investment securities held to maturity	(223,598)	(97,827)	0
Purchases of marketable equity securities	(26,166)	(2,818)	0
Proceeds from maturities of investment securities held to maturity	341,077	296,632	22
Proceeds from maturities of investment securities available for sale	2,345,512	1,664,730	1,842,563
Proceeds from Sale of Available-for-sale Securities	2,308,856	360,218	1,345,746
Proceeds from sales of marketable equity securities	56,749	9,528	0
Net change in overnight investments	(65,181)	601,979	586,279
Net Payment to the FDIC for Termination of Loss Share Agreements	(292)	(3,567)	(7,725)
Proceeds from Sale of Other Real Estate Held-for-investment	25,918	28,128	40,709
Proceeds from Sale of Property, Plant, and Equipment	132	1,721	3,061
Proceeds from sale of portfolio loans	24,247	9,591	162,649
Additions to premises and equipment	(121,077)	(140,444)	(84,798)
Business acquisitions, net of cash acquired	(236,728)	(155,126)	304,820
Net cash (used) provided by investing activities	(1,558,469)	97,573	(668,672)
FINANCING ACTIVITIES
Net change in time deposits	284,611	33,023	(538,250)
Net change in demand and other interest-bearing deposits	1,154,815	457,196	539,120
Net change in short-term borrowings	(27,703)	(246,517)	(44,680)
Proceeds from (Repayments of) Long-term Debt and Capital Securities	(73,284)	(752,447)	(6,955)
Origination of long-term obligations	200,000	125,000	175,000
Repurchase of common stock	(453,123)	(163,095)	0
Cash dividends paid	(18,137)	(16,779)	(14,412)
Net cash provided (used) by financing activities	1,067,179	(563,619)	109,823
Change in cash and due from banks	49,279	(8,710)	(203,591)
Cash and due from banks at beginning of period	327,440	336,150	539,741
Cash and due from banks at end of period	376,719	327,440	336,150
SUPPLEMENTAL DISCLOSURE OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Interest	78,230	37,097	43,639
Income taxes	83,038	73,806	88,565
Premises and equipment acquired through capital leases and other financing arrangements	14,639	23,375	34,980
Dividends declared but not paid	4,256	4,668	4,204
Unsettled maturities of investment securities	0	0	100,000
Unsettled sales of investment securities	0	0	208,464
Net reclassification of portfolio loans to (from) loans held for sale	22,034	(2,433)	161,719
Transfer of investment securities available for sale (from) to held to maturity	(2,080,617)
Transfer of investment securities available for sale (from) to held to maturity		2,485,761	0
Transfer of investment securities available for sale to marketable equity securities	0	107,578	0
Transfers of premises and equipment to other real estate	7,045	1,622	0
Transfers of premises and equipment to other real estate	0	12,196	5,327
Initial recognition of operating lease liabilities	0	$ (2,243)	$ 0
Initial recognition of operating lease assets	70,652
Initial recognition of operating lease liabilities	$ 71,793