CHANGES IN ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Realized (gains) losses on sales of investments	$ 63		$ 615		$ 764		$ 2,813
OTTI gross impairment losses	(39)	[1]	(3,470)	[1]	(462)	[1]	(4,969)	[1]
Income (loss) from continuing operations before income taxes	4,266		(1,009)		16,082		6,730
Tax effect	(1,080)		1,494		(4,777)		(221)
Citigroup's net income	3,227		468		11,217		6,345
Gain (loss) reclassified from AOCI
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Income (loss) from continuing operations before income taxes	286				416
Tax effect	(111)				(180)
Citigroup's net income	175				236
Realized gains (losses) on investment securities | Gain (loss) reclassified from AOCI
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Realized (gains) losses on sales of investments	(63)				(764)
OTTI gross impairment losses	39				270
Income (loss) from continuing operations before income taxes	(24)				(494)
Tax effect	9				170
Citigroup's net income	(15)				(324)
Cash flow hedges | Gain (loss) reclassified from AOCI
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Income (loss) from continuing operations before income taxes	249				720
Tax effect	(96)				(277)
Citigroup's net income	153				443
Cash flow hedges | Interest rate contracts | Gain (loss) reclassified from AOCI
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Income (loss) from continuing operations before income taxes	211				596
Cash flow hedges | Foreign exchange contracts | Gain (loss) reclassified from AOCI
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Income (loss) from continuing operations before income taxes	38				124
Pension liability adjustments | Gain (loss) reclassified from AOCI
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Amortization of unrecognized Prior service cost (benefit)	2				7
Amortization of unrecognized Net actuarial loss	61				205
Curtailment/settlement impact	(2)				(2)
Cumulative effect of change in accounting policy					(20)
Income (loss) from continuing operations before income taxes	61				190
Tax effect	(24)				(73)
Citigroup's net income	$ 37				$ 117

[1] Third quarter of 2012 included the recognition of a $3,340 million impairment charge related to the carrying value of Citi's remaining 35% interest in the Morgan Stanley Smith Barney joint venture (MSSB).The nine months of 2012 included the recognition of a $1,181 million impairment charge related to Citi's investment in Akbank. See Note 12 to the Consolidated Financial Statements.