REGULATORY CAPITAL AND CITIGROUP, INC. PARENT COMPANY INFORMATION - Regulatory Capital Compliance (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Required minimum, Tier 1 common capital (as a percent)	4.00%
Required minimum, Tier 1 capital ratio (as a percent)	5.50%
Well capitalized minimum, Tier 1 capital ratio (as a percent)	6.00%
Required minimum, Total capital ratio (as a percent)	8.00%
Well capitalized minimum, Total capital ratio (as a percent)	10.00%
Required minimum, Leverage ratio (as a percent)	4.00%
Well capitalized minimum, Leverage ratio (as a percent)	5.00%
Dividends received from Citibank N.A.	$ 8,900,000,000	$ 12,200,000,000
Citigroup Inc.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Common	166,663,000,000
Tier 1 Capital	166,663,000,000
Total Capital	184,959,000,000
Risk-weighted assets	1,274,672,000,000
Quarterly adjusted average total assets	1,849,325,000,000
Tier one common capital ratio (as a percent)	13.07%
Tier 1 Capital ratio (as a percent)	13.07%
Total Capital ratio (as a percent)	14.51%
Leverage ratio (as a percent)	9.01%
Citibank, N.A.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Common	128,262,000,000
Tier 1 Capital	128,262,000,000
Total Capital	139,246,000,000
Risk-weighted assets	945,407,000,000
Quarterly adjusted average total assets	1,366,910,000,000
Tier one common capital ratio (as a percent)	13.57%
Tier 1 Capital ratio (as a percent)	13.57%
Total Capital ratio (as a percent)	14.73%
Leverage ratio (as a percent)	9.38%
Citigroup Global Markets Inc.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Net capital or equivalent	5,521,000,000
Excess over minimum requirement	4,376,000,000
Citigroup Global Markets Limited
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Net capital or equivalent	7,162,000,000
Excess over minimum requirement	$ 2,482,000,000

Amount of leverage assets as calculated in accordance with U.S. Federal regulatory capital standards.

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Dividends that Citigroup received from Citibank during the current period.

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Tier 1 common capital, as defined by Supervisory Capital Assessment Program by U.S. banking regulators.

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Tier 1 common capital divided by risk weighted assets, as by Supervisory Capital Assessment Program by U.S. banking regulators.

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Tier One Common Capital Required for Capital Adequacy to Risk Weighted Assets

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The amount of total capital as defined in the regulations.

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The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The Total risk based capital ratio (total capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action.

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Total Capital divided by risk weighted assets as defined in the regulations.

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The amount of net capital in excess of the minimum required net capital.

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Net capital is equal to the net worth of the broker dealer, less certain items such as exchange memberships, carrying value of securities not readily marketable, haircuts on marketable securities in proprietary accounts, furniture and equipment and other illiquid assets as defined.

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Amount of risk-weighted assets as calculated in accordance with U.S. Federal regulatory capital standards.

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The minimum amount of Tier 1 Leverage Capital for capital adequacy purposes divided by average assets as defined in the regulations.

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The amount of Tier 1 Leverage Capital required to be categorized as well capitalized divided by average assets as defined in the regulatory framework for prompt corrective action.

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Tier 1 Leverage Capital divided by average assets as defined in the regulations.

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Tier 1 Risk Based Capital as defined in the regulations.

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The minimum Tier One Capital Ratio (Tier one capital divided by risk-weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The Tier 1 capital ratio (Tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized" under the regulatory framework for prompt corrective action.

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Tier 1 capital divided by risk weighted assets as defined by regulations.

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