Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 325,472	$ (148,749)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	21,743	22,869
Provision for credit losses	(49,095)	578,690
(Gain) loss on other real estate and foreclosed assets	(1,124)	9,252
Gain on sale of securities	(333)	(488)
Deferred tax expense (benefit)	1,378	(28,949)
Increase in cash surrender value of life insurance contracts	(21,122)	(14,443)
Impairment (gain) on disposal of assets	15,165	(556)
Loss on extinguishment of debt	4,165
Net (increase) decrease in loans held for sale	43,867	(46,691)
Net amortization of securities premium/discount	38,318	30,576
Amortization of intangible assets	12,746	15,302
Stock-based compensation expense	17,270	16,661
Net change in liability from variation margin collateral	53,387	(102,501)
Decrease in interest payable and other liabilities	22,037	11,369
(Increase) decrease in other assets	60,971	(97,265)
Other, net	(13,970)	(17,607)
Net cash provided by operating activities	530,875	227,470
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from the sale of available for sale securities	198,681	211,919
Proceeds from maturities of securities available for sale	831,433	662,269
Purchases of securities available for sale	(2,235,723)	(1,667,476)
Proceeds from maturities of securities held to maturity	99,044	169,863
Purchases of securities held to maturity	(59,362)	(20,884)
Net redemptions (purchases) of Federal Home Loan Bank stock	52,535	(12,868)
Net increase in short-term investments	(1,728,995)	(668,828)
Proceeds from sales of loans and leases	12,540	301,609
Net (increase) decrease in loans	915,652	(1,657,939)
Purchase of life insurance contracts	(75,000)
Proceeds from the surrender of life insurance contracts	44,045
Purchases of property and equipment	(12,402)	(31,214)
Proceeds from sales of other real estate	7,804	15,299
Other, net	35,903	8,456
Net cash used in investing activities	(1,913,845)	(2,689,794)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase in deposits	1,510,280	3,227,084
Net increase (decrease) in short-term borrowings	77,715	(807,977)
Proceeds from the issuance of long-term debt	22,388	166,425
Repayments of long-term debt	(153,365)	(230)
Dividends paid	(72,046)	(71,620)
Payroll tax remitted on net share settlement of equity awards	(1,298)	(1,639)
Proceeds from exercise of stock options	439
Proceeds from dividend reinvestment and stock purchase plans	2,940	3,098
Settlement of forward contract portion of accelerated share repurchase		12,110
Repurchase of shares	(2,509)	(12,716)
Net cash provided by financing activities	1,384,544	2,514,535
NET INCREASE IN CASH AND DUE FROM BANKS	1,574	52,211
CASH AND DUE FROM BANKS, BEGINNING	526,306	432,104
CASH AND DUE FROM BANKS, ENDING	527,880	484,315
SUPPLEMENTAL INFORMATION FOR NON-CASH INVESTING AND FINANCING ACTIVITIES
Assets acquired in settlement of loans	$ 2,623	$ 5,459