Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
OPERATING ACTIVITIES
Net income	$ 300,104	$ 210,955
Adjustments to reconcile net income to cash provided by operating activities:
Provision (credit) for loan and lease losses	(30,577)	48,907
Deferred tax expense (benefit)	13,441	17,774
Net change in current taxes	(805,084)	12,122
Depreciation and amortization	54,053	53,806
Net (decrease) increase in accrued interest payable	(603)	(4,012)
Net decrease (increase) in income earned not collected	12,651	(51,784)
Contribution to pension plans	0	(100,000)
Realized gains on investment securities available for sale, net	(25,037)	(33,547)
Marketable equity securities gains, net	(27,665)	(13,162)
Origination of loans held for sale	(631,104)	(503,190)
Proceeds from Sale of Loans Held-for-sale	562,399	474,153
Gain on sale of loans	(19,766)	(15,578)
Net (gains) losses on other real estate owned	(2,009)	2,475
Net accretion of premiums and discounts	1,490	20,889
Amortization of intangible assets	11,220	12,464
Origination of mortgage servicing rights, net of change in valuation allowance	(7,884)	357
Net change in other assets	19,040	(17,459)
Net change in other liabilities	(22,724)	(14,380)
Net cash provided by operating activities	(598,055)	100,790
INVESTING ACTIVITIES
Net increase in loans outstanding	136,009	(3,488,854)
Purchases of investment securities available for sale	(2,956,016)	(5,659,704)
Purchases of investment securities held to maturity	(1,012,009)	(803,307)
Purchases of marketable equity securities	(306)	(331,952)
Proceeds from maturities/calls of investment securities held to maturity	413,600	57,057
Proceeds from maturities/calls of investment securities available for sale	1,570,492	1,139,291
Proceeds from sales of investment securities available for sale	1,078,187	3,122,454
Proceeds from sales of marketable equity securities	1,111	313,131
Net increase in overnight investments	(3,524,046)	(1,964,602)
Cash paid to FDIC for settlement of shared-loss agreement	(16,103)	(99,468)
Proceeds from sales of other real estate	20,554	9,263
Proceeds from sales of premises and equipment	1,176	37
Purchases of premises and equipment	(51,282)	(62,721)
Business acquisitions, net of cash acquired	0	(59,999)
Other investing activities	(14,053)	0
Net cash used in investing activities	(4,352,686)	(7,829,374)
FINANCING ACTIVITIES
Net decrease in time deposits	(266,759)	(623,833)
Net increase in demand and other interest-bearing deposits	5,246,758	7,649,120
Net decrease in short-term borrowings	51,117	2,043
Repayments of Other Long-term Debt	(23,947)	(75,908)
Origination of long-term obligations	0	745,850
Net proceeds from preferred stock issuance	0	339,937
Repurchase of common stock	0	(282,923)
Cash dividends paid	(23,112)	(13,188)
Net cash (used in) provided by financing activities	4,984,057	7,741,098
Change in cash and due from banks	33,316	12,514
Cash and due from banks at beginning of period	362,048	376,719
Cash and due from banks at end of period	395,364	389,233
SUPPLEMENTAL DISCLOSURE OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Interest	31,706	61,061
Income taxes	867,196	38,453
Transfers of loans to other real estate	4,791	7,138
Dividends declared but not paid	0	4,007
Loans held for sale exchanged for investment securities	125,804	0
Reclassification of portfolio loans to loans held for sale	22,655	3,027
Transfers of premises and equipment to other real estate	6,549	2,046
Unsettled common stock repurchases	$ 0	$ 3,772