LOANS (Details 2) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Loans receivable
Loans, net of unearned income	$ 664,221,000,000	$ 665,472,000,000
Loans at fair value	5,729,000,000	5,029,000,000
Residential First Mortgage Loans | Loan to Values (LTVs)
Residential Mortgage Loan to Values
Loan, credit indicator ratio less than or equal to 80%	45,935,000,000	45,809,000,000
Loan, credit indicator ratio greater than 80% but less than or equal to 100%	14,938,000,000	13,458,000,000
Loan, credit indicator ratio greater than 100%	3,390,000,000	5,269,000,000
Residential First Mortgage Loans | Consumer Credit Scores (FICOs)
Consumer Loans Credit Quality Indicators, FICO score
Loan, credit score less than 620	11,858,000,000	11,860,000,000
Loan, credit score equal to or greater than 620 but less than 660	6,362,000,000	6,426,000,000
Loan, credit score equal to or greater than 660	45,872,000,000	46,207,000,000
Home equity loans | Loan to Values (LTVs)
Residential Mortgage Loan to Values
Loan, credit indicator ratio less than or equal to 80%	13,886,000,000	14,216,000,000
Loan, credit indicator ratio greater than 80% but less than or equal to 100%	8,643,000,000	8,685,000,000
Loan, credit indicator ratio greater than 100%	6,493,000,000	6,935,000,000
Home equity loans | Consumer Credit Scores (FICOs)
Consumer Loans Credit Quality Indicators, FICO score
Loan, credit score less than 620	3,917,000,000	4,093,000,000
Loan, credit score equal to or greater than 620 but less than 660	2,721,000,000	2,779,000,000
Loan, credit score equal to or greater than 660	22,510,000,000	23,152,000,000
Credit cards | Consumer Credit Scores (FICOs)
Consumer Loans Credit Quality Indicators, FICO score
Loan, credit score less than 620	8,089,000,000	8,125,000,000
Loan, credit score equal to or greater than 620 but less than 660	10,356,000,000	10,693,000,000
Loan, credit score equal to or greater than 660	87,392,000,000	94,437,000,000
Installment and other | Consumer Credit Scores (FICOs)
Consumer Loans Credit Quality Indicators, FICO score
Loan, credit score less than 620	3,868,000,000	3,900,000,000
Loan, credit score equal to or greater than 620 but less than 660	2,331,000,000	2,399,000,000
Loan, credit score equal to or greater than 660	5,029,000,000	5,186,000,000
Consumer
Loans receivable
Loans, current	368,970,000,000	376,904,000,000
Loans, 30-89 days past due	5,322,000,000	5,957,000,000
Loans, greater than or equal to 90 days past due	5,583,000,000	5,699,000,000
Loans, Past due government guaranteed	4,786,000,000	5,271,000,000
Loans, net of unearned income	384,661,000,000	393,831,000,000
Loans, total non-accrual	6,973,000,000	7,049,000,000
Loans, 90 days past due and accruing	5,487,000,000	5,880,000,000
Loans less than this number of days past due are considered current	30 days	30 days
Loans at fair value	933,000,000	957,000,000
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 | Loan to Values (LTVs)
Residential Mortgage Loan to Values
Loan, credit indicator ratio less than or equal to 80%	59,821,000,000	60,025,000,000
Loan, credit indicator ratio greater than 80% but less than or equal to 100%	23,581,000,000	22,143,000,000
Loan, credit indicator ratio greater than 100%	9,883,000,000	12,204,000,000
Consumer | Consumer Credit Scores (FICOs)
Consumer Loans Credit Quality Indicators, FICO score
Loan, credit score less than 620	27,732,000,000	27,978,000,000
Loan, credit score equal to or greater than 620 but less than 660	21,770,000,000	22,297,000,000
Loan, credit score equal to or greater than 660	160,803,000,000	168,982,000,000
Consumer | Residential First Mortgage Loans
Loans receivable
Loans at fair value	900,000,000	900,000,000
Delinquency status
Number of days past due, non-accrual status	90 days	90 days
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 | Other
Loans receivable
Loans, current	319,000,000	338,000,000
Loans, 30-89 days past due	10,000,000	13,000,000
Loans, greater than or equal to 90 days past due	15,000,000	16,000,000
Loans, net of unearned income	344,000,000	367,000,000
Loans, total non-accrual	39,000,000	43,000,000
Consumer | Total GCB and Citi Holdings Consumer
Loans receivable
Loans, current	368,651,000,000	376,566,000,000
Loans, 30-89 days past due	5,312,000,000	5,944,000,000
Loans, greater than or equal to 90 days past due	5,568,000,000	5,683,000,000
Loans, Past due government guaranteed	4,786,000,000	5,271,000,000
Loans, net of unearned income	384,317,000,000	393,464,000,000
Loans, total non-accrual	6,934,000,000	7,006,000,000
Loans, 90 days past due and accruing	5,487,000,000	5,880,000,000
Consumer | Unsecured Revolving Loans
Delinquency status
Number of days past due, non-accrual status	180 days	180 days
Consumer | In North America Offices
Loans receivable
Loans, current	224,007,000,000	232,386,000,000
Loans, 30-89 days past due	3,604,000,000	4,220,000,000
Loans, greater than or equal to 90 days past due	4,070,000,000	4,257,000,000
Loans, Past due government guaranteed	4,786,000,000	5,271,000,000
Loans, net of unearned income	236,467,000,000	246,134,000,000
Loans, total non-accrual	5,074,000,000	5,180,000,000
Loans, 90 days past due and accruing	5,057,000,000	5,467,000,000
Consumer | In North America Offices | Residential First Mortgage Loans
Loans receivable
Loans, current	66,901,000,000	66,666,000,000
Loans, 30-89 days past due	1,711,000,000	2,040,000,000
Loans, greater than or equal to 90 days past due	1,905,000,000	1,925,000,000
Loans, Past due government guaranteed	4,786,000,000	5,271,000,000
Loans, net of unearned income	75,303,000,000	75,902,000,000
Loans, total non-accrual	3,325,000,000	3,369,000,000
Loans, 90 days past due and accruing	3,704,000,000	3,997,000,000
Loans, 30-89 days past due, guaranteed by U.S. government-sponsored agencies	1,000,000,000	1,200,000,000
Loans, greater than or equal to 90 days past due, guaranteed by U.S. government-sponsored agencies	3,700,000,000	4,100,000,000
Consumer | In North America Offices | Home equity loans
Loans receivable
Loans, current	29,811,000,000	30,603,000,000
Loans, 30-89 days past due	361,000,000	434,000,000
Loans, greater than or equal to 90 days past due	566,000,000	605,000,000
Loans, net of unearned income	30,738,000,000	31,642,000,000
Loans, total non-accrual	1,408,000,000	1,452,000,000
Consumer | In North America Offices | Credit cards
Loans receivable
Loans, current	106,556,000,000	113,878,000,000
Loans, 30-89 days past due	1,328,000,000	1,495,000,000
Loans, greater than or equal to 90 days past due	1,340,000,000	1,456,000,000
Loans, net of unearned income	109,224,000,000	116,829,000,000
Loans, 90 days past due and accruing	1,340,000,000	1,456,000,000
Consumer | In North America Offices | Installment and other
Loans receivable
Loans, current	12,056,000,000	12,609,000,000
Loans, 30-89 days past due	185,000,000	225,000,000
Loans, greater than or equal to 90 days past due	239,000,000	243,000,000
Loans, net of unearned income	12,480,000,000	13,077,000,000
Loans, total non-accrual	243,000,000	247,000,000
Loans, 90 days past due and accruing	4,000,000	7,000,000
Consumer | In North America Offices | Commercial market loans
Loans receivable
Loans, current	8,683,000,000	8,630,000,000
Loans, 30-89 days past due	19,000,000	26,000,000
Loans, greater than or equal to 90 days past due	20,000,000	28,000,000
Loans, net of unearned income	8,722,000,000	8,684,000,000
Loans, total non-accrual	98,000,000	112,000,000
Loans, 90 days past due and accruing	9,000,000	7,000,000
Consumer | In offices outside North America
Loans receivable
Loans, current	144,644,000,000	144,180,000,000
Loans, 30-89 days past due	1,708,000,000	1,724,000,000
Loans, greater than or equal to 90 days past due	1,498,000,000	1,426,000,000
Loans, net of unearned income	147,850,000,000	147,330,000,000
Loans, total non-accrual	1,860,000,000	1,826,000,000
Loans, 90 days past due and accruing	430,000,000	413,000,000
Consumer | In offices outside North America | Residential First Mortgage Loans
Loans receivable
Loans, current	46,712,000,000	46,067,000,000
Loans, 30-89 days past due	394,000,000	435,000,000
Loans, greater than or equal to 90 days past due	318,000,000	332,000,000
Loans, net of unearned income	47,424,000,000	46,834,000,000
Loans, total non-accrual	583,000,000	584,000,000
Consumer | In offices outside North America | Credit cards
Loans receivable
Loans, current	33,728,000,000	34,733,000,000
Loans, 30-89 days past due	795,000,000	780,000,000
Loans, greater than or equal to 90 days past due	655,000,000	641,000,000
Loans, net of unearned income	35,178,000,000	36,154,000,000
Loans, total non-accrual	414,000,000	402,000,000
Loans, 90 days past due and accruing	430,000,000	413,000,000
Consumer | In offices outside North America | Installment and other
Loans receivable
Loans, current	30,709,000,000	30,138,000,000
Loans, 30-89 days past due	414,000,000	398,000,000
Loans, greater than or equal to 90 days past due	164,000,000	158,000,000
Loans, net of unearned income	31,287,000,000	30,694,000,000
Loans, total non-accrual	242,000,000	230,000,000
Consumer | In offices outside North America | Commercial market loans
Loans receivable
Loans, current	33,495,000,000	33,242,000,000
Loans, 30-89 days past due	105,000,000	111,000,000
Loans, greater than or equal to 90 days past due	361,000,000	295,000,000
Loans, net of unearned income	33,961,000,000	33,648,000,000
Loans, total non-accrual	$ 621,000,000	$ 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