LOANS AND LEASES - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accrued interest receivable on loans and leases held for investment	$ 841		$ 820
Loans pledged as collateral for FHLB borrowed funds	152,671		154,679
Interest income on direct financing lease	12	$ 11
Retail \| Residential mortgages \| Pledged as collateral for FHLB borrowing capacity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans pledged as collateral for FHLB borrowed funds	36,700		38,400
Consumer and Commercial Portfolio Segment \| Auto, commercial and commercial real estate loans \| Notes Payable, Other Payables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans pledged as collateral for FHLB borrowed funds	$ 36,200		$ 34,800

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No definition available.

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- Definition

Amount of interest income from net investment in direct financing lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482964/270-10-50-6A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479773/842-30-50-5

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- Definition

Amortized cost excluding accrued interest, after allowance for credit loss, of financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479344/326-20-45-1

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- Definition

Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 946
-SubTopic 310
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480833/946-310-45-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3)(a)(4))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

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