Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ (148,749)	$ 235,248
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	22,869	22,867
Provision for credit losses	578,690	38,552
Loss on other real estate and foreclosed assets	9,252	852
Gain on sale of securities	(488)
Deferred tax expense (benefit)	(28,949)	30,136
Increase in cash surrender value of life insurance contracts	(14,443)	(10,792)
(Gain) loss on disposal of other assets	(556)	70
Net increase in loans held for sale	(46,691)	(46,727)
Net amortization of securities premium/discount	30,576	23,133
Amortization of intangible assets	15,302	15,074
Stock-based compensation expense	16,661	15,497
Net change in liability from variation margin collateral	(102,501)	(42,500)
Contribution to pension plan		(100,000)
Increase (decrease) in interest payable and other liabilities	11,369	(1,632)
Increase in other assets	(97,265)	(10,631)
Other, net	(17,607)	(2,854)
Net cash provided by operating activities	227,470	166,293
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from the sale of available for sale securities	211,919	143,334
Proceeds from maturities of securities available for sale	662,269	204,391
Purchases of securities available for sale	(1,667,476)	(810,198)
Proceeds from maturities of securities held to maturity	169,863	297,150
Purchases of securities held to maturity	(20,884)	(183,626)
Net (increase) decrease in short-term investments	(668,828)	383,970
Proceeds from sales of loans and leases	301,609	111,141
Net increase in loans	(1,657,939)	(353,971)
Purchase of life insurance contracts		(32,788)
Purchases of property and equipment	(31,214)	(33,746)
Proceeds from sales of other real estate	15,299	20,764
Cash acquired in stock-based business combination		28,060
Final cash settlement for acquisition of business		(1,112)
Other, net	(4,412)	(19,815)
Net cash used in investing activities	(2,689,794)	(246,446)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase (decrease) in deposits	3,227,084	(229,964)
Net increase (decrease) in short-term borrowings	(807,977)	452,691
Proceeds from the issuance of long-term debt, net of issuance costs	166,425	11,649
Repayments of long-term debt	(230)	(226)
Dividends paid	(71,620)	(70,771)
Payroll tax remitted on net share settlement of equity awards	(1,639)	(1,594)
Proceeds from exercise of stock options		367
Proceeds from dividend reinvestment and stock purchase plans	3,098	2,692
Settlement of forward contract portion of accelerated share repurchase	12,110
Repurchase of shares	(12,716)
Net cash provided by financing activities	2,514,535	164,844
NET INCREASE IN CASH AND DUE FROM BANKS	52,211	84,691
CASH AND DUE FROM BANKS, BEGINNING	432,104	383,372
CASH AND DUE FROM BANKS, ENDING	484,315	468,063
SUPPLEMENTAL INFORMATION FOR NON-CASH INVESTING AND FINANCING ACTIVITIES
Value of stock-based consideration in business combination		193,849
Assets acquired in settlement of loans	$ 5,459	$ 14,170