Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
OPERATING ACTIVITIES
Net income	$ 491,723	$ 457,371	$ 400,313
Adjustments to reconcile net income to cash provided by operating activities:
Provision for credit losses	58,352	31,441	28,468
Deferred tax expense (benefit)	(25,535)	54,598	(13,377)
Change in current taxes payable	(5,894)	(19,564)	23,353
Depreciation	108,641	103,828	96,781
Change in accrued interest payable	(8,683)	14,412	(240)
Change in income earned not collected	(21,982)	(4,151)	(10,785)
Gain on acquisitions	(100,000)	(3,592)	(50,000)
Realized gains on investment securities available for sale, net	(60,253)	(7,115)	(351)
Marketable equity securities (gains) losses, net	(29,395)	(20,625)	7,610
Gain on extinguishment of debt	0	0	(26,553)
Origination of loans held for sale	(1,078,096)	(736,015)	(593,307)
Proceeds from sale of loans held for sale	1,045,937	731,803	608,549
Gain on sale of loans	(37,594)	(15,183)	(11,210)
Loss on sale of other real estate	4,056	2,664	4,390
Net amortization of premiums and discounts	(8,513)	(27,263)	(32,291)
Amortization of intangible assets	32,801	23,861	23,648
Net change in other liabilities	(12,149)	(5,927)	(5,258)
Net change in other assets	(7,286)	(24,274)	(5,076)
Net change in other liabilities	(6,115)	(15,992)	9,105
Net cash provided by operating activities	340,015	540,277	453,769
INVESTING ACTIVITIES
Net change in loans outstanding	(3,803,188)	(1,282,880)	(1,023,885)
Payments to Acquire Available-for-sale Securities	(8,678,543)	(4,705,038)	(1,451,287)
Purchases of investment securities held to maturity	(1,633,165)	(223,598)	(97,827)
Purchases of marketable equity securities	(333,140)	(26,166)	(2,818)
Proceeds from maturities of investment securities held to maturity	301,347	341,077	296,632
Proceeds from maturities of investment securities available for sale	2,791,291	2,345,512	1,664,730
Proceeds from Sale of Available-for-sale Securities	4,585,002	2,308,856	360,218
Proceeds from sales of marketable equity securities	352,835	56,749	9,528
Net change in overnight investments	(3,204,363)	(65,181)	601,979
Proceeds from sale of portfolio loans	13,368	24,247	9,591
Net Payment to the FDIC for Termination of Loss Share Agreements	(99,468)	0	0
Proceeds from Sale of Other Real Estate Held-for-investment	28,280	25,918	28,128
Proceeds from Sale of Property, Plant, and Equipment	1,369	132	1,721
Additions to premises and equipment	(133,384)	(121,077)	(140,444)
Business acquisitions, net of cash acquired	(59,999)	(236,728)	(155,126)
Net cash (used) provided by investing activities	(9,871,758)	(1,558,177)	101,140
FINANCING ACTIVITIES
Net change in time deposits	(1,010,190)	284,611	33,023
Net change in demand and other interest-bearing deposits	9,989,107	1,154,815	457,196
Net change in short-term borrowings	(96,746)	(27,703)	(246,517)
Repayment of long-term obligations	(86,737)	(73,284)	(752,447)
Origination of long-term obligations	400,000	200,000	125,000
Net proceeds from subordinated notes issuance	345,849	0	0
Net proceeds from preferred stock issuance	339,937	0	0
Repurchase of common stock	(333,755)	(453,123)	(163,095)
Cash dividends paid	(30,393)	(18,137)	(16,779)
Net cash provided (used) by financing activities	9,517,072	1,067,179	(563,619)
Change in cash and due from banks	(14,671)	49,279	(8,710)
Cash and due from banks at beginning of period	376,719	327,440	336,150
Cash and due from banks at end of period	362,048	376,719	327,440
SUPPLEMENTAL DISCLOSURE OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Interest	104,567	78,230	37,097
Income taxes	116,583	83,038	73,806
Premises and equipment acquired through finance leases and other financing arrangements	11,635	14,639	23,375
Dividends declared but not paid	4,613	4,256	4,668
Net reclassification of portfolio loans from (to) loans held for sale	1,687	22,034	(2,433)
Transfer of investment securities available for sale to (from) held to maturity		(2,080,617)
Transfer of investment securities available for sale to (from) held to maturity	1,460,745		2,485,761
Transfer of investment securities available for sale to marketable equity securities	0	0	107,578
Transfers of premises and equipment to other real estate	15,187	7,045	1,622
Transfers of premises and equipment to other real estate	0	0	12,196
Common Stock Repurchases, Unsettled	$ 0	$ 0	$ 2,243