LOANS (Details 3) (USD $)	6 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Consumer	Jun. 30, 2012 Consumer	Jun. 30, 2013 Consumer	Jun. 30, 2012 Consumer	Dec. 31, 2012 Consumer	Sep. 30, 2012 Consumer New OCC guidance	Jun. 30, 2013 Consumer Residential First Mortgage Loans	Jun. 30, 2012 Consumer Residential First Mortgage Loans	Jun. 30, 2013 Consumer Residential First Mortgage Loans	Jun. 30, 2012 Consumer Residential First Mortgage Loans	Dec. 31, 2012 Consumer Residential First Mortgage Loans	Sep. 30, 2012 Consumer Residential First Mortgage Loans New OCC guidance	Jun. 30, 2013 Consumer Home equity loans	Jun. 30, 2012 Consumer Home equity loans	Jun. 30, 2013 Consumer Home equity loans	Jun. 30, 2012 Consumer Home equity loans	Dec. 31, 2012 Consumer Home equity loans	Sep. 30, 2012 Consumer Home equity loans New OCC guidance	Jun. 30, 2013 Consumer Credit cards	Jun. 30, 2012 Consumer Credit cards	Jun. 30, 2013 Consumer Credit cards	Jun. 30, 2012 Consumer Credit cards	Dec. 31, 2012 Consumer Credit cards	Jun. 30, 2013 Consumer Individual installment and other	Jun. 30, 2012 Consumer Individual installment and other	Jun. 30, 2013 Consumer Individual installment and other	Jun. 30, 2012 Consumer Individual installment and other	Dec. 31, 2012 Consumer Individual installment and other	Jun. 30, 2013 Consumer Commercial market loans	Jun. 30, 2012 Consumer Commercial market loans	Jun. 30, 2013 Consumer Commercial market loans	Jun. 30, 2012 Consumer Commercial market loans	Dec. 31, 2012 Consumer Commercial market loans
LOANS
Maximum period of loan modification under Citi's short-term modification programs	12 months
Financing receivable impaired
Recorded investment in receivables reclassified to TDR as a result of new guidance issued by OCC							$ 1,714,000,000						$ 1,327,000,000						$ 387,000,000
Recorded investment		24,641,000,000		24,641,000,000		29,640,000,000		17,323,000,000		17,323,000,000		20,870,000,000		2,032,000,000		2,032,000,000		2,135,000,000		3,774,000,000		3,774,000,000		4,584,000,000	1,093,000,000		1,093,000,000		1,612,000,000	419,000,000		419,000,000		439,000,000
Unpaid principal balance		26,508,000,000		26,508,000,000		31,783,000,000		18,287,000,000		18,287,000,000		22,062,000,000		2,637,000,000		2,637,000,000		2,727,000,000		3,820,000,000		3,820,000,000		4,639,000,000	1,117,000,000		1,117,000,000		1,618,000,000	647,000,000		647,000,000		737,000,000
Related specific allowance		5,293,000,000		5,293,000,000		6,941,000,000		2,656,000,000		2,656,000,000		3,585,000,000		532,000,000		532,000,000		636,000,000		1,384,000,000		1,384,000,000		1,800,000,000	619,000,000		619,000,000		860,000,000	102,000,000		102,000,000		60,000,000
Average carrying value				28,067,000,000		29,592,000,000				19,657,000,000		19,956,000,000				2,090,000,000		1,911,000,000				4,412,000,000		5,272,000,000			1,453,000,000		1,958,000,000			455,000,000		495,000,000
Interest income recognized		328,000,000	373,000,000	684,000,000	764,000,000			207,000,000	209,000,000	424,000,000	423,000,000			18,000,000	17,000,000	39,000,000	32,000,000			61,000,000	78,000,000	126,000,000	166,000,000		34,000,000	60,000,000	83,000,000	130,000,000		8,000,000	9,000,000	12,000,000	13,000,000
Impaired financing receivable without specific allowance								2,095,000,000		2,095,000,000		2,344,000,000		416,000,000		416,000,000		378,000,000												175,000,000		175,000,000		183,000,000
Smaller-balance impaired consumer loans modified since January 1, 2008, dollar amount		24,200,000,000		24,200,000,000		29,200,000,000
Amounts of such outstanding modified consumer loans, including those modified prior to 2008		$ 25,000,000,000		$ 25,000,000,000		$ 30,100,000,000