REGULATORY CAPITAL AND CITIGROUP, INC. PARENT COMPANY INFORMATION - Condensed Cash Flow Statements (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in ) operating activities of continuing operations	$ 45,434	$ 63,244	$ (10,362)
Cash flows from investing activities of continuing operations
Purchases of investments	(258,992)us-gaap_PaymentsToAcquireInvestments	(220,823)us-gaap_PaymentsToAcquireInvestments	(256,907)us-gaap_PaymentsToAcquireInvestments
Proceeds from sales of investments	135,824	131,100	143,853
Proceeds from maturities of investments	94,117	84,831	102,020
Net cash provided by (used in) investing activities of continuing operations	29,491	(91,338)	30,335
Cash flows from financing activities of continuing operations
Dividends paid	(633)us-gaap_PaymentsOfDividends	(314)us-gaap_PaymentsOfDividends	(143)us-gaap_PaymentsOfDividends
Issuance of preferred stock	3,699	4,192	2,250
Net cash provided by (used in) financing activities of continuing operations	(70,270)	23,094	(12,501)
Change in cash and due from banks	2,223	(6,568)	7,752
Cash and due from banks at beginning of period	29,885us-gaap_CashAndDueFromBanks	36,453us-gaap_CashAndDueFromBanks	28,701us-gaap_CashAndDueFromBanks
Cash and due from banks at end of period	32,108us-gaap_CashAndDueFromBanks	29,885us-gaap_CashAndDueFromBanks	36,453us-gaap_CashAndDueFromBanks
Supplemental disclosure of cash flow information for continuing operations
Cash paid during the year for income taxes	4,632us-gaap_IncomeTaxesPaidNet	4,495us-gaap_IncomeTaxesPaidNet	3,900us-gaap_IncomeTaxesPaidNet
Cash paid during the year for interest	12,868us-gaap_InterestPaidNet	14,383us-gaap_InterestPaidNet	19,739us-gaap_InterestPaidNet
Citigroup Inc.
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in ) operating activities of continuing operations	5,940	(7,881)	1,598
Cash flows from investing activities of continuing operations
Purchases of investments	0	0	(5,701)
Proceeds from sales of investments	41	385	37,056
Proceeds from maturities of investments	155	233	4,286
Changes in investments and advances—intercompany	(7,986)	7,226	(397)
Other investing activities	5	4	994
Net cash provided by (used in) investing activities of continuing operations	(7,785)	7,848	36,238
Cash flows from financing activities of continuing operations
Dividends paid	(633)	(314)	(143)
Issuance of preferred stock	3,699	4,192	2,250
Proceeds (repayments) from issuance of long-term debt—third-party, net	(3,636)	(13,426)	(33,434)
Net change in short-term borrowings and other advances—intercompany	3,297	11,402	(6,160)
Other financing activities	(990)	(1,741)	(199)
Net cash provided by (used in) financing activities of continuing operations	1,737	113	(37,686)
Change in cash and due from banks	(108)	80	150
Cash and due from banks at beginning of period	233	153	3
Cash and due from banks at end of period	125	233	153
Supplemental disclosure of cash flow information for continuing operations
Cash paid during the year for income taxes	235	(71)	78
Cash paid during the year for interest	$ 5,632	$ 6,514	$ 7,883

Represents the intercompany changes in investments and advances during the period.

No definition available.

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This element represents proceeds from (repayment of) short-term debt of affiliates, subsidiaries and holding companies.

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Amount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Includes effect from exchange rate changes.

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For banks and other depository institutions: Includes cash on hand (currency and coin), cash items in process of collection, noninterest bearing deposits due from other financial institutions (including corporate credit unions), and noninterest bearing balances with the Federal Reserve Banks, Federal Home Loan Banks and central banks.

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The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

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The amount of cash paid for interest during the period net of cash paid for interest that is capitalized.

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Amount of cash inflow (outflow) of financing activities, excluding discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

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Amount of cash inflow (outflow) of investing activities, excluding discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.

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Amount of cash inflow (outflow) from operating activities, excluding discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.

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The net cash outflow or inflow from other investing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.

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Cash outflow in the form of capital distributions and dividends to common shareholders, preferred shareholders and noncontrolling interests.

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The cash outflow associated with the purchase of all investments (debt, security, other) during the period.

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Proceeds from issuance of capital stock which provides for a specific dividend that is paid to the shareholders before any dividends to common stockholders and which takes precedence over common stockholders in the event of liquidation.

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The cash inflow associated with the maturity (principal being due), prepayment and call (request of early payment) of other investments not otherwise defined in the taxonomy.

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The net cash inflow or outflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.

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Amount of cash inflow (outflow) from long-term debt, including capital lease obligations and mandatory redeemable capital securities.

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The cash inflow associated with the sale of other investments not otherwise defined in the taxonomy.

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