LOANS (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended				12 Months Ended
	Sep. 30, 2014 Q		Sep. 30, 2013		Sep. 30, 2014 Q		Sep. 30, 2013		Dec. 31, 2013 Q
Financing receivable impaired
Maximum period of loan modification under Citi's short-term modification programs					12 months
Consumer
Financing receivable impaired
Recorded investment	$ 21,203	[1],[2]			$ 21,203	[1],[2]			$ 23,793	[1],[3]
Unpaid principal balance	23,023				23,023				25,727
Related specific allowance	4,192	[4]			4,192	[4]			4,633	[4]
Average carrying value					22,661	[5]			24,950	[6]
Interest income recognized	266	[7],[8]	298	[7],[8]	848	[7],[8]	982	[7],[8]
Number of quarters used to calculate the average recorded investment balance	4				4				4
Consumer | Residential first mortgages
Financing receivable impaired
Recorded investment	15,237	[1],[2]			15,237	[1],[2]			16,801	[1],[3]
Unpaid principal balance	16,148				16,148				17,788
Related specific allowance	2,108	[4]			2,108	[4]			2,309	[4]
Average carrying value					16,202	[5]			17,616	[6]
Interest income recognized	167	[7],[8]	179	[7],[8]	532	[7],[8]	604	[7],[8]
Impaired financing receivable without specific allowance	1,957				1,957				2,169
Consumer | Home equity loans
Financing receivable impaired
Recorded investment	2,058	[1],[2]			2,058	[1],[2]			2,141	[1],[3]
Unpaid principal balance	2,701				2,701				2,806
Related specific allowance	546	[4]			546	[4]			427	[4]
Average carrying value					2,103	[5]			2,116	[6]
Interest income recognized	18	[7],[8]	23	[7],[8]	56	[7],[8]	61	[7],[8]
Impaired financing receivable without specific allowance	555				555				568
Consumer | Credit cards
Financing receivable impaired
Recorded investment	2,584	[1],[2]			2,584	[1],[2]			3,339	[1],[3]
Unpaid principal balance	2,626				2,626				3,385
Related specific allowance	898	[4]			898	[4]			1,178	[4]
Average carrying value					2,965	[5]			3,720	[6]
Interest income recognized	47	[7],[8]	56	[7],[8]	148	[7],[8]	182	[7],[8]
Consumer | Individual installment and other
Financing receivable impaired
Recorded investment	969	[1],[2]			969	[1],[2]			1,114	[1],[3]
Unpaid principal balance	983				983				1,143
Related specific allowance	447	[4]			447	[4]			536	[4]
Average carrying value					1,016	[5]			1,094	[6]
Interest income recognized	31	[7],[8]	35	[7],[8]	94	[7],[8]	118	[7],[8]
Consumer | Commercial market loans
Financing receivable impaired
Recorded investment	355	[1],[2]			355	[1],[2]			398	[1],[3]
Unpaid principal balance	565				565				605
Related specific allowance	193	[4]			193	[4]			183	[4]
Average carrying value					375	[5]			404	[6]
Interest income recognized	3	[7],[8]	5	[7],[8]	18	[7],[8]	17	[7],[8]
Impaired financing receivable without specific allowance	$ 112				$ 112				$ 111

[1] Recorded investment in a loan includes net deferred loan fees and costs, unamortized premium or discount and direct write-downs and includes accrued interest only on credit card loans.

[2] $1,957 million of residential first mortgages, $555 million of home equity loans and $112 million of commercial market loans do not have a specific allowance.

[3] $2,169 million of residential first mortgages, $568 million of home equity loans and $111 million of commercial market loans do not have a specific allowance.

[4] Included in the Allowance for loan losses.

[5] Average carrying value represents the average recorded investment ending balance for the last four quarters and does not include the related specific allowance.

[6] Average carrying value represents the average recorded investment ending balance for last four quarters and does not include the related specific allowance.

[7] Includes amounts recognized on both an accrual and cash basis.

[8] Cash interest receipts on smaller-balance homogeneous loans are generally recorded as revenue. The interest recognition policy for commercial market loans is identical to that for corporate loans, as described below.