LOANS - Non-Accrual Corporate Loans (Details) - Corporate loans - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Financing Receivable, Impaired [Line Items]
Recorded investment	$ 1,016		$ 953
Related specific allowance	417		323
Non-accrual loans for which there is no ACLL	941		1,048
Interest income recognized	13	$ 8
Commercial and industrial
Financing Receivable, Impaired [Line Items]
Recorded investment	897		788
Related specific allowance	365		295
Non-accrual loans for which there is no ACLL	306		353
Financial institutions
Financing Receivable, Impaired [Line Items]
Recorded investment	10		0
Related specific allowance	2		0
Non-accrual loans for which there is no ACLL	114		65
Mortgage and real estate
Financing Receivable, Impaired [Line Items]
Recorded investment	20		44
Related specific allowance	4		4
Non-accrual loans for which there is no ACLL	500		583
Lease financing
Financing Receivable, Impaired [Line Items]
Non-accrual loans for which there is no ACLL	0		0
Other
Financing Receivable, Impaired [Line Items]
Recorded investment	89		121
Related specific allowance	46		24
Non-accrual loans for which there is no ACLL	$ 21		$ 47

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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