Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
OPERATING ACTIVITIES
Net income (loss)	$ 92,643	$ (3,439)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Provision for credit losses	(7,500)	88,000
Net amortization (accretion) of premiums and discounts from acquisition	117	(275)
Depreciation and amortization	14,042	15,591
Amortization of debt issuance costs	113
Deferred income tax expense (benefit)	10,246	(11,134)
Net increase in trading securities and other earning assets	(9,350)	(15,559)
Losses (gains) on investment securities, net	8,336	(3,520)
Gains on sales of assets	(4,298)	(1,922)
Amortization of securities premiums, net of discount accretion	14,876	8,792
Originations of loans held for sale	(45,128)	(77,129)
Gains on sales of loans held for sale, net	(1,602)	(320)
Proceeds from sales of loans held for sale	43,163	75,667
Equity-based compensation	5,152	3,410
Net tax benefit related to equity compensation plans	1,079	312
Changes in:
Accrued income	4,156	12,629
Accrued expenses and taxes	(88,201)	(2,803)
Other assets and liabilities, net	78,096	(79,008)
Net cash provided by operating activities	115,940	9,292
Securities held to maturity:
Maturities, calls and principal repayments	49,520	19,497
Purchases	(77,576)	(17,555)
Securities available for sale:
Sales	129,128	84,439
Maturities, calls and principal repayments	520,441	310,159
Purchases	(1,322,855)	(421,966)
Equity securities with readily determinable fair values:
Purchases	(226)
Equity securities without readily determinable fair values:
Maturities, calls and principal repayments	2,177	3,725
Purchases	(7,144)	(1,081)
Payment on low-income housing tax credit investment commitments	(1,173)	(4,039)
Net increase in loans	(398,795)	(525,091)
Net decrease in fed funds sold and resell agreements	20,522	793,595
Net cash activity from acquisitions and divestitures	16,623	24
Net increase in interest-bearing balances due from other financial institutions	(11,347)	(1,274)
Purchases of premises and equipment	(5,958)	(17,652)
Proceeds from sales of premises and equipment	73	8,389
Proceeds from bank-owned and company-owned life insurance death benefit		19
Net cash (used in) provided by investing activities	(1,086,590)	231,189
FINANCING ACTIVITIES
Net increase (decrease) in demand and savings deposits	1,441,071	(186,380)
Net decrease in time deposits	(211,530)	(241,344)
Net increase (decrease) in fed funds purchased and repurchase agreements	444,321	(5,591)
Proceeds from short-term debt		15,000
Cash dividends paid	(15,456)	(15,150)
Proceeds from exercise of stock options and sales of treasury shares	12,237	2,454
Purchases of treasury stock	(4,027)	(59,386)
Net cash provided by (used in) financing activities	1,666,616	(490,397)
Increase (decrease) in cash and cash equivalents	695,966	(249,916)
Cash and cash equivalents at beginning of period	3,497,566	1,669,170
Cash and cash equivalents at end of period	4,193,532	1,419,254
Supplemental disclosures:
Income tax payments (refunds)	622	(1,530)
Total interest payments	$ 14,337	42,134
Noncash disclosures:
Acquisition of low-income housing tax credit investments		27,834
Commitment to fund low-income housing tax credit investments		$ 27,834