LOANS (Details 2) (USD $)	9 Months Ended			12 Months Ended
	Sep. 30, 2014		Sep. 30, 2013	Dec. 31, 2013
Delinquency status
Loans, net of unearned income	$ 653,826,000,000			$ 665,472,000,000
Loans at fair value	4,411,000,000			5,029,000,000
Residential first mortgages | Consumer Credit Scores (FICOs)
Consumer Loans Credit Quality Indicators, FICO score
Loan, credit score less than 620	9,862,000,000	[1],[2]		11,860,000,000	[1],[3]
Loan, credit score equal to or greater than 620 but less than 660	5,861,000,000	[1],[2]		6,426,000,000	[1],[3]
Loan, credit score equal to or greater than 660	47,538,000,000	[1],[2]		46,207,000,000	[1],[3]
Residential first mortgages | Loan to Values (LTVs)
Residential Mortgage Loan to Values
Loan, credit indicator ratio less than or equal to 80%	50,801,000,000	[3],[4]		45,809,000,000	[3],[4]
Loan, credit indicator ratio greater than 80% but less than or equal to 100%	9,667,000,000	[3],[4]		13,458,000,000	[3],[4]
Loan, credit indicator ratio greater than 100%	2,975,000,000	[3],[4]		5,269,000,000	[3],[4]
Home equity loans | Consumer Credit Scores (FICOs)
Consumer Loans Credit Quality Indicators, FICO score
Loan, credit score less than 620	3,386,000,000	[1],[2]		4,093,000,000	[1],[3]
Loan, credit score equal to or greater than 620 but less than 660	2,527,000,000	[1],[2]		2,779,000,000	[1],[3]
Loan, credit score equal to or greater than 660	21,577,000,000	[1],[2]		23,152,000,000	[1],[3]
Home equity loans | Loan to Values (LTVs)
Residential Mortgage Loan to Values
Loan, credit indicator ratio less than or equal to 80%	15,129,000,000	[3],[4]		14,216,000,000	[3],[4]
Loan, credit indicator ratio greater than 80% but less than or equal to 100%	7,647,000,000	[3],[4]		8,685,000,000	[3],[4]
Loan, credit indicator ratio greater than 100%	4,591,000,000	[3],[4]		6,935,000,000	[3],[4]
Credit cards | Consumer Credit Scores (FICOs)
Consumer Loans Credit Quality Indicators, FICO score
Loan, credit score less than 620	7,283,000,000	[1],[2]		8,125,000,000	[1],[3]
Loan, credit score equal to or greater than 620 but less than 660	9,963,000,000	[1],[2]		10,693,000,000	[1],[3]
Loan, credit score equal to or greater than 660	88,770,000,000	[1],[2]		94,437,000,000	[1],[3]
Installment and other | Consumer Credit Scores (FICOs)
Consumer Loans Credit Quality Indicators, FICO score
Loan, credit score less than 620	3,312,000,000	[1],[2]		3,900,000,000	[1],[3]
Loan, credit score equal to or greater than 620 but less than 660	2,888,000,000	[1],[2]		2,399,000,000	[1],[3]
Loan, credit score equal to or greater than 660	5,376,000,000	[1],[2]		5,186,000,000	[1],[3]
Consumer
Delinquency status
Number of days past due, non-accrual status	60 days		60 days
Loans, current	362,449,000,000	[5],[6]		376,887,000,000	[5],[7]
Loans, 30-89 days past due	4,962,000,000	[8]		5,944,000,000	[8]
Loans, greater than or equal to 90 days past due	4,858,000,000	[8]		5,729,000,000	[8]
Loans, Past due government guaranteed	4,049,000,000	[9]		5,271,000,000	[10]
Loans, net of unearned income	376,318,000,000	[6]		393,831,000,000	[7]
Loans, total non-accrual	6,272,000,000			7,095,000,000
Loans, 90 days past due and accruing	4,704,000,000			5,876,000,000
Loans less than this number of days past due are considered current	30 days			30 days
Consumer | Minimum
Delinquency status
Minimum number of payments made consecutively for the loans to be re-aged	1			1
Consumer | Maximum
Delinquency status
Minimum number of payments made consecutively for the loans to be re-aged	3			3
Consumer | Consumer Credit Scores (FICOs)
Consumer Loans Credit Quality Indicators, FICO score
Loan, credit score less than 620	23,843,000,000	[1],[2]		27,978,000,000	[1],[3]
Loan, credit score equal to or greater than 620 but less than 660	21,239,000,000	[1],[2]		22,297,000,000	[1],[3]
Loan, credit score equal to or greater than 660	163,261,000,000	[1],[2]		168,982,000,000	[1],[3]
Consumer | Loan to Values (LTVs)
Residential Mortgage Loan to Values
Loan, credit indicator ratio less than or equal to 80%	65,930,000,000	[3],[4]		60,025,000,000	[3],[4]
Loan, credit indicator ratio greater than 80% but less than or equal to 100%	17,314,000,000	[3],[4]		22,143,000,000	[3],[4]
Loan, credit indicator ratio greater than 100%	7,566,000,000	[3],[4]		12,204,000,000	[3],[4]
Consumer | Residential first mortgages
Delinquency status
Number of days past due, non-accrual status	90 days			90 days
Loans at fair value	45,000,000			900,000,000
Consumer | Home equity loans
Delinquency status
Number of days past due, non-accrual status	90 days			90 days
Consumer | Credit cards
Delinquency status
Number of days past due, non-accrual status	180 days			180 days
Consumer | Installment and other
Delinquency status
Number of days past due, non-accrual status	90 days			90 days
Consumer | Commercial market loans
Delinquency status
Number of days past due, non-accrual status	90 days			90 days
Consumer | Total GCB and Citi Holdings Consumer
Delinquency status
Loans, current	362,173,000,000	[5],[6]		376,520,000,000	[5],[7]
Loans, 30-89 days past due	4,962,000,000	[8]		5,944,000,000	[8]
Loans, greater than or equal to 90 days past due	4,858,000,000	[8]		5,729,000,000	[8]
Loans, Past due government guaranteed	4,049,000,000	[9]		5,271,000,000	[10]
Loans, net of unearned income	376,042,000,000	[6]		393,464,000,000	[7]
Loans, total non-accrual	6,239,000,000			7,052,000,000
Loans, 90 days past due and accruing	4,704,000,000			5,876,000,000
Consumer | Other
Delinquency status
Loans, current	276,000,000	[5],[6]		367,000,000	[5],[7]
Loans, 30-89 days past due	0	[8]		0	[8]
Loans, greater than or equal to 90 days past due	0	[8]		0	[8]
Loans, net of unearned income	276,000,000	[6]		367,000,000	[7]
Loans, total non-accrual	33,000,000			43,000,000
Consumer | Unsecured Revolving Loans
Delinquency status
Number of days past due, non-accrual status	180 days			180 days
Consumer | In North America Offices
Delinquency status
Loans, current	220,845,000,000	[5],[6]		232,340,000,000	[5],[7]
Loans, 30-89 days past due	3,486,000,000	[8]		4,220,000,000	[8]
Loans, greater than or equal to 90 days past due	3,511,000,000	[8]		4,303,000,000	[8]
Loans, Past due government guaranteed	4,049,000,000	[9]		5,271,000,000	[10]
Loans, net of unearned income	231,891,000,000	[6]		246,134,000,000	[7]
Loans, total non-accrual	4,539,000,000			5,226,000,000
Loans, 90 days past due and accruing	4,368,000,000			5,463,000,000
Consumer | In North America Offices | Residential first mortgages
Delinquency status
Loans, current	64,838,000,000	[5],[6]		66,612,000,000	[5],[7]
Loans, 30-89 days past due	1,585,000,000	[8]		2,044,000,000	[8]
Loans, greater than or equal to 90 days past due	1,532,000,000	[8]		1,975,000,000	[8]
Loans, Past due government guaranteed	4,049,000,000	[9]		5,271,000,000	[10]
Loans, net of unearned income	72,004,000,000	[6]		75,902,000,000	[7]
Loans, total non-accrual	2,912,000,000			3,415,000,000
Loans, 90 days past due and accruing	3,167,000,000			3,997,000,000
Loans, 30-89 days past due, guaranteed by U.S. government-sponsored agencies	800,000,000			1,200,000,000
Loans, greater than or equal to 90 days past due, guaranteed by U.S. government-sponsored agencies	3,200,000,000			4,100,000,000
Consumer | In North America Offices | Home equity loans
Delinquency status
Loans, current	28,130,000,000	[11],[5],[6]		30,603,000,000	[11],[5],[7]
Loans, 30-89 days past due	344,000,000	[11],[8]		434,000,000	[11],[8]
Loans, greater than or equal to 90 days past due	521,000,000	[11],[8]		605,000,000	[11],[8]
Loans, net of unearned income	28,995,000,000	[11],[6]		31,642,000,000	[11],[7]
Loans, total non-accrual	1,285,000,000	[11]		1,452,000,000	[11]
Consumer | In North America Offices | Credit cards
Delinquency status
Loans, current	107,015,000,000	[5],[6]		113,886,000,000	[5],[7]
Loans, 30-89 days past due	1,295,000,000	[8]		1,491,000,000	[8]
Loans, greater than or equal to 90 days past due	1,189,000,000	[8]		1,452,000,000	[8]
Loans, net of unearned income	109,499,000,000	[6]		116,829,000,000	[7]
Loans, 90 days past due and accruing	1,189,000,000			1,452,000,000
Consumer | In North America Offices | Installment and other
Delinquency status
Loans, current	12,344,000,000	[5],[6]		12,609,000,000	[5],[7]
Loans, 30-89 days past due	229,000,000	[8]		225,000,000	[8]
Loans, greater than or equal to 90 days past due	255,000,000	[8]		243,000,000	[8]
Loans, net of unearned income	12,828,000,000	[6]		13,077,000,000	[7]
Loans, total non-accrual	251,000,000			247,000,000
Loans, 90 days past due and accruing	4,000,000			7,000,000
Consumer | In North America Offices | Commercial market loans
Delinquency status
Loans, current	8,518,000,000	[5],[6]		8,630,000,000	[5],[7]
Loans, 30-89 days past due	33,000,000	[8]		26,000,000	[8]
Loans, greater than or equal to 90 days past due	14,000,000	[8]		28,000,000	[8]
Loans, net of unearned income	8,565,000,000	[6]		8,684,000,000	[7]
Loans, total non-accrual	91,000,000			112,000,000
Loans, 90 days past due and accruing	8,000,000			7,000,000
Consumer | In offices outside North America
Delinquency status
Loans, current	141,328,000,000	[5],[6]		144,180,000,000	[5],[7]
Loans, 30-89 days past due	1,476,000,000	[8]		1,724,000,000	[8]
Loans, greater than or equal to 90 days past due	1,347,000,000	[8]		1,426,000,000	[8]
Loans, net of unearned income	144,151,000,000	[6]		147,330,000,000	[7]
Loans, total non-accrual	1,700,000,000			1,826,000,000
Loans, 90 days past due and accruing	336,000,000			413,000,000
Consumer | In offices outside North America | Residential first mortgages
Delinquency status
Loans, current	45,957,000,000	[5],[6]		46,067,000,000	[5],[7]
Loans, 30-89 days past due	311,000,000	[8]		435,000,000	[8]
Loans, greater than or equal to 90 days past due	234,000,000	[8]		332,000,000	[8]
Loans, net of unearned income	46,502,000,000	[6]		46,834,000,000	[7]
Loans, total non-accrual	489,000,000			584,000,000
Consumer | In offices outside North America | Credit cards
Delinquency status
Loans, current	31,147,000,000	[5],[6]		34,733,000,000	[5],[7]
Loans, 30-89 days past due	685,000,000	[8]		780,000,000	[8]
Loans, greater than or equal to 90 days past due	575,000,000	[8]		641,000,000	[8]
Loans, net of unearned income	32,407,000,000	[6]		36,154,000,000	[7]
Loans, total non-accrual	445,000,000			402,000,000
Loans, 90 days past due and accruing	336,000,000			413,000,000
Consumer | In offices outside North America | Installment and other
Delinquency status
Loans, current	30,988,000,000	[5],[6]		30,138,000,000	[5],[7]
Loans, 30-89 days past due	377,000,000	[8]		398,000,000	[8]
Loans, greater than or equal to 90 days past due	166,000,000	[8]		158,000,000	[8]
Loans, net of unearned income	31,531,000,000	[6]		30,694,000,000	[7]
Loans, total non-accrual	240,000,000			230,000,000
Consumer | In offices outside North America | Commercial market loans
Delinquency status
Loans, current	33,236,000,000	[5],[6]		33,242,000,000	[5],[7]
Loans, 30-89 days past due	103,000,000	[8]		111,000,000	[8]
Loans, greater than or equal to 90 days past due	372,000,000	[8]		295,000,000	[8]
Loans, net of unearned income	33,711,000,000	[6]		33,648,000,000	[7]
Loans, total non-accrual	$ 526,000,000			$ 610,000,000
Open-ended consumer loans
Delinquency status
Minimum number of payments made consecutively for the loans to be re-aged	3			3
Number of re-age modification limitations in twelve months	1			1
Number of re-age modification limitations in five years	2			2

[1] Excludes balances where FICO was not available. Such amounts are not material.

[2] Excludes loans guaranteed by U.S. government entities, loans subject to long-term standby commitments (LTSCs) with U.S. government-sponsored entities and loans recorded at fair value.

[3] Excludes loans guaranteed by U.S. government entities, loans subject to LTSCs with U.S. government-sponsored entities and loans recorded at fair value.

[4] Excludes balances where LTV was not available. Such amounts are not material.

[5] Loans less than 30 days past due are presented as current.

[6] Includes $45 million of residential first mortgages recorded at fair value.

[7] Includes $0.9 billion of residential first mortgages recorded at fair value.

[8] Excludes loans guaranteed by U.S. government-sponsored entities.

[9] Consists of residential first mortgages that are guaranteed by U.S. government-sponsored entities that are 30-89 days past due of $0.8 billion and 90 days past due of $3.2 billion.

[10] Consists of residential first mortgages that are guaranteed by U.S. government-sponsored entities that are 30-89 days past due of $1.2 billion and 90 days past due of $4.1 billion.

[11] Fixed rate home equity loans and loans extended under home equity lines of credit, which are typically in junior lien positions.