LOANS - Non-Accrual Corporate Loans (Details) - Corporate loans - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024
Financing Receivable, Impaired [Line Items]
Recorded investment	$ 666	$ 660
Related specific allowance	177	302
Non-accrual loans for which there is no ACLL	710	717
Interest income recognized	8	7	$ 18
Commercial and industrial
Financing Receivable, Impaired [Line Items]
Recorded investment	228	199
Related specific allowance	75	86
Non-accrual loans for which there is no ACLL	383	343
Financial institutions
Financing Receivable, Impaired [Line Items]
Recorded investment	0	0
Related specific allowance	0	0
Non-accrual loans for which there is no ACLL	74	73
Mortgage and real estate
Financing Receivable, Impaired [Line Items]
Recorded investment	389	276
Related specific allowance	61	42
Non-accrual loans for which there is no ACLL	220	291
Lease financing
Financing Receivable, Impaired [Line Items]
Non-accrual loans for which there is no ACLL	21	0
Other
Financing Receivable, Impaired [Line Items]
Recorded investment	49	185
Related specific allowance	41	174
Non-accrual loans for which there is no ACLL	$ 12	$ 10

Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Nonaccrual

No definition available.

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Namespace Prefix:	c_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable on nonaccrual status. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-16

+ Details

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Period Type:	instant

- Definition

Amortized cost excluding accrued interest, of financing receivable on nonaccrual status with no allowance for credit loss. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-16

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Amount of interest income on financing receivable on nonaccrual status.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-16

+ Details

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