RETIREMENT BENEFITS (Details 5) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Postemployment Plans	Sep. 30, 2012 Postemployment Plans	Sep. 30, 2013 Postemployment Plans	Sep. 30, 2012 Postemployment Plans
Net Expense
Benefits earned during the period					$ 6,000,000	$ 5,000,000	$ 19,000,000	$ 17,000,000
Interest cost on benefit obligation					3,000,000	4,000,000	9,000,000	11,000,000
Amortization of unrecognized
Prior service cost (benefit)					1,000,000	2,000,000	5,000,000	6,000,000
Net actuarial loss					4,000,000	3,000,000	10,000,000	9,000,000
Total service related expense					14,000,000	14,000,000	43,000,000	43,000,000
Non-service related expense					7,000,000	7,000,000	20,000,000	19,000,000
Total net (benefit) expense					21,000,000	21,000,000	63,000,000	62,000,000
Defined Contribution Pension and Other Postretirement Plans Disclosure
Maximum percentage contribution by employer of employees eligible pay			6.00%	6.00%
Maximum compensation to be eligible for fixed contribution from employer			100,000
Percentage of fixed contribution by employer, for eligible employees whose compensation is $100,000 or less			2.00%
Pretax expense associated with Citigroup 401(k) plan	$ 96,000,000	$ 98,000,000	$ 298,000,000	$ 294,000,000