LOANS (Details 3) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
LOANS
Maximum period of loan modification under Citi's short-term modification programs (in months)	12		12
Dollar amount of loans included under Citi's short-term modification programs	$ 4,000,000,000		$ 4,000,000,000
Consumer
Financing receivable impaired
Recorded investment	29,747,000,000		29,747,000,000		27,328,000,000
Unpaid principal balance	31,291,000,000		31,291,000,000		28,731,000,000
Related specific allowance	8,874,000,000		8,874,000,000		7,730,000,000
Average carrying value	27,423,000,000		27,423,000,000		24,466,000,000
Interest income recognized	461,000,000	500,000,000	851,000,000	881,000,000
Smaller-balance impaired consumer loans modified since January 1, 2008, dollar amount	29,100,000,000		29,100,000,000		26,600,000,000
Amounts of such outstanding modified consumer loans, including those modified prior to 2008	30,400,000,000		30,400,000,000		28,200,000,000
Consumer | Credit cards
Financing receivable impaired
Recorded investment	6,326,000,000		6,326,000,000		5,906,000,000
Unpaid principal balance	6,394,000,000		6,394,000,000		5,906,000,000
Related specific allowance	2,984,000,000		2,984,000,000		3,237,000,000
Average carrying value	5,767,000,000		5,767,000,000		5,314,000,000
Interest income recognized	101,000,000		198,000,000
Consumer | Residential First Mortgage Loans
Financing receivable impaired
Recorded investment	18,358,000,000		18,358,000,000		16,225,000,000
Unpaid principal balance	19,499,000,000		19,499,000,000		17,287,000,000
Related specific allowance	3,414,000,000		3,414,000,000		2,783,000,000
Average carrying value	16,330,000,000		16,330,000,000		13,606,000,000
Interest income recognized	253,000,000		454,000,000
Impaired financing receivable without specific allowance	797,000,000		797,000,000		1,050,000,000
Smaller-balance impaired consumer loans modified since January 1, 2008, dollar amount		1,050,000,000		1,050,000,000
Consumer | Home equity loans
Financing receivable impaired
Recorded investment	1,714,000,000		1,714,000,000		1,205,000,000
Unpaid principal balance	1,762,000,000		1,762,000,000		1,256,000,000
Related specific allowance	1,061,000,000		1,061,000,000		393,000,000
Average carrying value	1,301,000,000		1,301,000,000		1,010,000,000
Interest income recognized	18,000,000		30,000,000
Impaired financing receivable without specific allowance	7,000,000		7,000,000		6,000,000
Consumer | Individual installment and other
Financing receivable impaired
Recorded investment	2,739,000,000		2,739,000,000		3,286,000,000
Unpaid principal balance	2,782,000,000		2,782,000,000		3,348,000,000
Related specific allowance	1,335,000,000		1,335,000,000		1,172,000,000
Average carrying value	3,288,000,000		3,288,000,000		3,627,000,000
Interest income recognized	82,000,000		152,000,000
Consumer | Commercial market loans
Financing receivable impaired
Recorded investment	610,000,000		610,000,000		706,000,000
Unpaid principal balance	854,000,000		854,000,000		934,000,000
Related specific allowance	80,000,000		80,000,000		145,000,000
Average carrying value	737,000,000		737,000,000		909,000,000
Interest income recognized	7,000,000		17,000,000
Impaired financing receivable without specific allowance	$ 217,000,000		$ 217,000,000		$ 323,000,000