CHANGES IN ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Realized gains on sales of investments	$ 450		$ 1,925
OTTI gross impairment losses	(261)	[1]	(1,327)	[1]
Income from continuing operations before income taxes	5,553		4,068
Tax effect	(1,588)		(1,006)
Citigroup's net income	3,808		2,931
Amounts reclassified from AOCI
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Income from continuing operations before income taxes	491
Tax effect	(175)
Citigroup's net income	316
Realized gains (losses) on investment securities | Amounts reclassified from AOCI
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Realized gains on sales of investments	450
OTTI gross impairment losses	(261)
Income from continuing operations before income taxes	189
Tax effect	(59)
Citigroup's net income	130
Cash flow hedges | Amounts reclassified from AOCI
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Income from continuing operations before income taxes	226
Tax effect	(87)
Citigroup's net income	139
Cash flow hedges | Interest rate contracts | Amounts reclassified from AOCI
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Income from continuing operations before income taxes	183
Cash flow hedges | Foreign exchange contracts | Amounts reclassified from AOCI
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Income from continuing operations before income taxes	43
Pension liability adjustments | Amounts reclassified from AOCI
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Amortization of prior service costs	3
Amortization of prior of actuarial gains (losses)	73
Income from continuing operations before income taxes	76
Tax effect	(29)
Citigroup's net income	47
Foreign currency translation adjustment | Amounts reclassified from AOCI
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Citigroup's net income	$ 0

[1] The first quarter 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.