Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 327,380	$ 323,770	$ 215,632
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	30,902	26,532	28,142
Provision for credit losses	47,708	36,116	58,968
(Gain) loss on sale other real estate and foreclosed assets	626	(3,355)	(2,839)
Deferred tax expense	47,100	45,214	49,831
Increase in cash surrender value of life insurance contracts	(16,158)	(7,850)	(14,959)
Gain on sale of Visa Class B common shares		(33,229)
Loss on sale of securities available for sale		25,480
(Gain) loss on the sale of loans	(619)	6,991	(3,363)
Loss on sale of business		1,145
Loss on disposal of other assets	1,109	1,897	1,587
Net (increase) decrease in loans held for sale	(27,773)	11,986	3,317
Net amortization of securities premium/discount	32,166	33,161	33,244
Amortization of intangibles	20,844	22,050	22,417
Amortization of FDIC loss share receivable			2,427
Stock-based compensation expense	20,902	19,793	17,633
Contribution to pension plan	(100,000)	(39,000)
Increase (decrease) in interest payable and other liabilities	(1,753)	(9,397)	2,307
Net payments from FDIC for loss share claims			2,299
Decrease in FDIC loss share receivable			8,613
Increase in other assets	(22,556)	(13,811)	(9,836)
Other, net	(7,929)	1,691	(4,335)
Net cash provided by operating activities	351,949	449,184	411,085
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from sales of securities available for sale	268,413	455,162	213,877
Proceeds from maturities of securities available for sale	294,681	327,141	338,843
Purchases of securities available for sale	(1,010,805)	(629,976)	(742,279)
Proceeds from maturities of securities held to maturity	417,520	359,312	373,088
Purchases of securities held to maturity	(183,626)	(375,770)	(863,457)
Net (increase) decrease in short-term investments	281,251	(18,710)	351,087
Proceeds from sale of loans	112,048	166,462	59,483
Net increase in loans	(555,008)	(1,358,077)	(1,051,628)
Purchase of life insurance contracts	(32,788)	(1,822)	(50,000)
Proceeds from the sale of Visa Class B shares		42,858
Purchases of property and equipment	(42,716)	(50,664)	(20,297)
Proceeds from sales of other real estate	30,658	17,214	24,324
Cash acquired in stock-based business combination	28,059
Consideration (paid) received in business combinations	(1,112)	141,769	476,609
Proceeds from the sale of business, net of cash sold		77,648
Other, net	(65,597)	551	(4,971)
Net cash used in investing activities	(459,022)	(846,902)	(895,321)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase (decrease) in deposits	(627,557)	679,669	900,427
Net increase (decrease) in short-term borrowings	1,058,748	(114,762)	(118,151)
Repayments of long-term debt	(14,222)	(90,216)	(204,111)
Issuance of long-term debt	20,846	20,610	165
Dividends paid	(94,871)	(88,838)	(83,266)
Payroll tax remitted on net share settlement of equity awards	(6,295)	(8,695)	(11,881)
Repurchase of common stock	(185,000)	(8,267)
Proceeds from exercise of stock options	542	1,232	12,092
Proceeds from dividend reinvestment and stock purchase plan	3,614	3,409	3,220
Net cash provided by financing activities	155,805	394,142	498,495
NET INCREASE (DECREASE) IN CASH AND DUE FROM BANKS	48,732	(3,576)	14,259
CASH AND DUE FROM BANKS, BEGINNING	383,372	386,948	372,689
CASH AND DUE FROM BANKS, ENDING	432,104	383,372	386,948
SUPPLEMENTAL INFORMATION
Income taxes paid	28,288	7,283	45,092
Interest paid	232,456	175,382	108,702
SUPPLEMENTAL INFORMATION FOR NON-CASH INVESTING AND FINANCING ACTIVITIES
Assets acquired in settlement of loans	$ 21,285	$ 22,393	$ 19,140