ALLOWANCE FOR CREDIT LOSSES ON LOANS AND FINANCE LEASES - Carrying Amount of Portfolios (Parenthetical) (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable Allowance For Credit Losses [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 11,777,289	$ 9,002,205
Commercial Portfolio Segment [Member] \| COVID-19 [Member] \| Small Business Administration [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Financing Receivable, before Allowance for Credit Loss	$ 406,000

Amount, before allowance for credit loss, of financing receivable.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 79
-URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922352-210448

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 5
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Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 80
-URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922355-210448

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