Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
OPERATING ACTIVITIES
Net income	$ 180,055	$ 57,090
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	16,500	109,500
Net amortization (accretion) of premiums and discounts from acquisition	251	(176)
Depreciation and amortization	27,714	31,054
Amortization of debt issuance costs	225
Deferred income tax expense (benefit)	825	(16,990)
Net increase in trading securities and other earning assets	(19,006)	(5,765)
Gains on investment securities, net	(7,119)	(8,099)
Gains on sales of assets	(3,358)	(1,767)
Amortization of securities premiums, net of discount accretion	29,373	19,986
Originations of loans held for sale	(83,962)	(298,732)
Gains on sales of loans held for sale, net	(3,242)	(810)
Proceeds from sales of loans held for sale	88,609	299,132
Equity-based compensation	9,304	6,702
Net tax benefit related to equity compensation plans	1,743	279
Changes in:
Accrued income	4,501	(2,454)
Accrued expenses and taxes	(61,192)	22,535
Other assets and liabilities, net	(3,964)	(109,842)
Net cash provided by operating activities	177,257	101,643
Securities held to maturity:
Maturities, calls and principal repayments	110,262	59,010
Purchases	(179,657)	(57,838)
Securities available for sale:
Sales	176,802	250,609
Maturities, calls and principal repayments	957,564	1,256,575
Purchases	(2,322,572)	(2,296,485)
Equity securities with readily determinable fair values:
Sales	72,801
Purchases	(508)
Equity securities without readily determinable fair values:
Maturities, calls and principal repayments	2,499	6,792
Purchases	(11,928)	(4,213)
Payment on low-income housing tax credit investment commitments	(5,695)	(5,482)
Net increase in loans	(846,915)	(1,888,618)
Net decrease in fed funds sold and resell agreements	503,814	230,702
Net cash activity from acquisitions and divestitures	18,431	24
Net (increase) decrease in interest-bearing balances due from other financial institutions	(29,066)	550
Purchases of premises and equipment	(15,391)	(35,361)
Proceeds from sales of premises and equipment	1,828	8,420
Purchases of bank-owned and company-owned life insurance	(100,000)
Proceeds from bank-owned and company-owned life insurance death benefit		1,474
Net cash used in investing activities	(1,667,731)	(2,473,841)
FINANCING ACTIVITIES
Net increase in demand and savings deposits	3,195,002	3,290,366
Net decrease in time deposits	(197,782)	(434,206)
Net increase in fed funds purchased and repurchase agreements	467,892	67,186
Proceeds from short-term debt		15,000
Cash dividends paid	(30,935)	(30,040)
Proceeds from exercise of stock options and sales of treasury shares	14,425	2,779
Purchases of treasury stock	(4,088)	(59,459)
Net cash provided by financing activities	3,444,514	2,851,626
Increase in cash and cash equivalents	1,954,040	479,428
Cash and cash equivalents at beginning of period	3,497,566	1,669,170
Cash and cash equivalents at end of period	5,451,606	2,148,598
Supplemental disclosures:
Income tax payments	48,003	17,399
Total interest payments	24,388	59,584
Noncash disclosures:
Acquisition of low-income housing tax credit investments	12,622	47,172
Commitment to fund low-income housing tax credit investments	$ 12,622	$ 47,172