Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 195,890	$ (228,105)
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	14,352	15,420
Provision for credit losses	(22,140)	553,691
(Gain) loss on other real estate and foreclosed assets	(627)	9,790
Gain on sale of securities	(333)	(112)
Deferred tax expense (benefit)	2,158	(48,786)
Increase in cash surrender value of life insurance contracts	(15,353)	(4,235)
Impairment of or loss on disposal of assets	15,274	19
Loss on extinguishment of debt	4,165
Net (increase) decrease in loans held for sale	45,414	(53,176)
Net amortization of securities premium/discount	26,211	19,208
Amortization of intangible assets	8,664	10,514
Stock-based compensation expense	11,646	11,086
Net change in liability from variation margin collateral	44,441	(113,616)
Decrease in interest payable and other liabilities	(6,229)	(4,493)
(Increase) decrease in other assets	45,301	(86,813)
Other, net	(1,271)	(13,512)
Net cash provided by operating activities	367,563	66,880
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from the sale of available for sale securities	198,681	124,122
Proceeds from maturities of securities available for sale	593,760	385,125
Purchases of securities available for sale	(2,235,723)	(582,655)
Proceeds from maturities of securities held to maturity	77,197	124,037
Purchases of securities held to maturity	(59,362)	(12,359)
Net increase in short-term investments	(869,999)	(649,965)
Proceeds from sales of loans and leases	12,312	22,221
Net (increase) decrease in loans	670,795	(2,029,351)
Purchase of life insurance contracts	(75,000)
Proceeds from the surrender of life insurance contracts	44,045
Purchases of property and equipment	(7,636)	(19,607)
Proceeds from sales of other real estate	5,504	7,678
Other, net	6,549	(10,361)
Net cash used in investing activities	(1,638,877)	(2,641,115)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase in deposits	1,575,231	3,518,693
Net decrease in short-term borrowings	(151,005)	(959,997)
Proceeds from the issuance of long-term debt	22,388	166,812
Repayments of long-term debt	(153,287)	(153)
Dividends paid	(48,044)	(47,817)
Payroll tax remitted on net share settlement of equity awards	(1,082)	(1,585)
Proceeds from exercise of stock options	439
Proceeds from dividend reinvestment and stock purchase plans	1,962	2,018
Settlement of forward contract portion of accelerated share repurchase		12,110
Repurchase of shares		(12,716)
Net cash provided by financing activities	1,246,602	2,677,365
NET INCREASE (DECREASE) IN CASH AND DUE FROM BANKS	(24,712)	103,130
CASH AND DUE FROM BANKS, BEGINNING	526,306	432,104
CASH AND DUE FROM BANKS, ENDING	501,594	535,234
SUPPLEMENTAL INFORMATION FOR NON-CASH INVESTING AND FINANCING ACTIVITIES
Assets acquired in settlement of loans	$ 2,578	$ 5,459