Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 323,770	$ 215,632	$ 149,296
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	26,532	28,142	28,363
Provision for loan losses	36,116	58,968	110,659
Gain on other real estate owned	(3,355)	(2,839)	(4,444)
Deferred tax (benefit) expense	45,214	49,831	(7,839)
Increase in cash surrender value of life insurance contracts	(7,850)	(14,959)	(11,112)
Gain on sale of Visa Class B common shares	(33,229)
(Gain) loss on sales of securities available for sale	25,480		(1,754)
(Gain) loss on the sale of loans	6,991	(3,363)	(4,414)
Loss on sale of business	1,145
(Gain) loss on disposal of other assets	1,897	1,587	(3,426)
Net (increase) decrease in loans held for sale	11,986	3,317	(14,267)
Net amortization of securities premium/discount	33,161	33,244	29,048
Amortization of intangibles	22,050	22,417	19,781
Amortization of FDIC loss share receivable		2,427	5,918
Stock-based compensation expense	19,793	17,633	14,266
Contribution to pension plan	(39,000)		(15,000)
Increase (decrease) in interest payable and other liabilities	(9,397)	2,307	10,315
Net payments (to) from FDIC for loss share claims		2,299	(3,134)
Decrease in FDIC loss share receivable		8,613	5,667
(Increase) decrease in other assets	(13,811)	(9,836)	15,197
Other, net	1,691	(4,335)	20,795
Net cash provided by operating activities	449,184	411,085	343,915
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from sales of securities available for sale	455,162	213,877	173,215
Proceeds from maturities of securities available for sale	327,141	338,843	408,311
Purchases of securities available for sale	(629,976)	(742,279)	(1,071,869)
Proceeds from maturities of securities held to maturity	359,312	373,088	425,453
Purchases of securities held to maturity	(375,770)	(863,457)	(563,661)
Net (increase) decrease in short-term investments	(18,710)	351,087	487,378
Proceeds from sale of loans	166,462	59,483	177,645
Net increase in loans	(1,358,077)	(1,051,628)	(1,331,125)
Purchase of life insurance contracts	(1,822)	(50,000)	(40,000)
Purchases of property and equipment	(50,664)	(20,297)	(19,272)
Proceeds from the sale of Visa Class B shares	42,858
Proceeds from sales of property and equipment	60	1,853	7,445
Proceeds from sales of other real estate	17,214	24,324	24,624
Cash received in excess of cash paid for acquisitions	141,769	476,609
Proceeds from the sale of business, net of cash sold	77,648
Other, net	491	(6,824)	825
Net cash used in investing activities	(846,902)	(895,321)	(1,321,031)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase in deposits	679,669	900,427	1,075,370
Net decrease in short-term borrowings	(114,762)	(118,151)	(198,238)
Repayments of long-term debt	(90,216)	(204,111)	(21,271)
Issuance of long-term debt	20,610	165	6,838
Dividends paid	(88,838)	(83,266)	(76,551)
Payroll tax remitted on net share settlement of equity awards	(8,695)	(11,881)	(3,178)
Repurchase of common stock	(8,267)
Proceeds from exercise of stock options	1,232	12,092	2,147
Proceeds from issuance of common stock in public offering			259,299
Proceeds from dividend reinvestment and stock purchase plan	3,409	3,220	1,515
Net cash provided by financing activities	394,142	498,495	1,045,931
NET INCREASE (DECREASE) IN CASH AND DUE FROM BANKS	(3,576)	14,259	68,815
CASH AND DUE FROM BANKS, BEGINNING	386,948	372,689	303,874
CASH AND DUE FROM BANKS, ENDING	383,372	386,948	372,689
SUPPLEMENTAL INFORMATION
Income taxes paid	7,283	45,092	30,184
Interest paid	175,382	108,702	69,624
SUPPLEMENTAL INFORMATION FOR NON-CASH INVESTING AND FINANCING ACTIVITIES
Assets acquired in settlement of loans	$ 22,393	$ 19,140	$ 16,314