DEBT - Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument
Weighted average interest rate	3.87%
Long-term debt, at fair value	$ 231,999	$ 236,709
Weighted average interest rate after effect of derivative contract	3.84%
Senior debt
Debt Instrument
Long-term debt, at fair value	$ 205,695	208,010
Subordinated debt
Debt Instrument
Long-term debt, at fair value	24,593	26,987
Trust preferred securities
Debt Instrument
Long-term debt, at fair value	1,711	1,712
Citigroup Inc.
Debt Instrument
Long-term debt, at fair value	$ 143,768
Citigroup Inc. \| Senior debt
Debt Instrument
Weighted average interest rate	3.40%
Long-term debt, at fair value	$ 117,511	123,488
Citigroup Inc. \| Subordinated debt
Debt Instrument
Weighted average interest rate	4.70%
Long-term debt, at fair value	$ 24,545	26,963
Citigroup Inc. \| Trust preferred securities
Debt Instrument
Weighted average interest rate	8.44%
Long-term debt, at fair value	$ 1,711	1,712
Bank
Debt Instrument
Long-term debt, at fair value	$ 61,237
Bank \| Senior debt
Debt Instrument
Weighted average interest rate	2.71%
Long-term debt, at fair value	$ 61,237	65,856
Collateralized long-term advances from Federal Home Loan Bank	10,500	19,300
Broker-dealer
Debt Instrument
Long-term debt, at fair value	$ 26,994
Broker-dealer \| Senior debt
Debt Instrument
Weighted average interest rate	3.25%
Long-term debt, at fair value	$ 26,947	18,666
Broker-dealer \| Subordinated debt
Debt Instrument
Weighted average interest rate	5.35%
Long-term debt, at fair value	$ 48	$ 24

Represents the weighted average interest rate at the end of the period after the effect of the derivative contract.

No definition available.

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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.

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- Definition

Including both current and noncurrent portions, Federal Home Loan Bank borrowings initially due beyond one year or beyond the normal operating cycle if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Weighted average interest rate of long-term debt outstanding calculated at point in time.

+ References

No definition available.

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