CHANGES IN ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Reclassification out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Realized (gains) losses on sales of investments	$ (186)	$ (307)
Income from continuing operations before income taxes	(4,987)	(6,937)
Tax effect	1,479	2,120
Income (loss) from continuing operations	(3,508)	(4,817)
Realized gains (losses) on investment securities
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Total amounts reclassified out of AOCI, after-tax	8	(151)
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	(186)	(307)
OTTI gross impairment losses	203	72
Income from continuing operations before income taxes	17	(235)
Tax effect	(9)	84
Income (loss) from continuing operations	8	(151)
Debt valuation adjustment (DVA)
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Total amounts reclassified out of AOCI, after-tax	1
Debt valuation adjustment (DVA) \| (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	1	0
Income from continuing operations before income taxes	1	0
Tax effect	0	0
Income (loss) from continuing operations	1	0
Cash flow hedges
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Total amounts reclassified out of AOCI, after-tax	26	54
Cash flow hedges \| (Gain) loss reclassified from AOCI
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Income from continuing operations before income taxes	42	86
Tax effect	(16)	(32)
Income (loss) from continuing operations	26	54
Cash flow hedges \| (Gain) loss reclassified from AOCI \| Interest rate contracts
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Income from continuing operations before income taxes	16	46
Cash flow hedges \| (Gain) loss reclassified from AOCI \| Foreign exchange contracts
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Income from continuing operations before income taxes	26	40
Pension liability adjustments
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Total amounts reclassified out of AOCI, pretax	54	64
Total tax effect	(19)	(23)
Total amounts reclassified out of AOCI, after-tax	35	41
Prior service cost (benefit)
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Total amounts reclassified out of AOCI, pretax	(10)	(11)
Net actuarial loss
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Total amounts reclassified out of AOCI, pretax	66	75
Curtailment/settlement impact
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Total amounts reclassified out of AOCI, pretax	2	0
Foreign currency translation adjustment
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Total amounts reclassified out of AOCI, after-tax	0	0
Foreign currency translation adjustment \| (Gain) loss reclassified from AOCI
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Income (loss) from continuing operations	0	0
Citigroup's accumulated other comprehensive income (loss)
Pretax and after-tax amounts reclassified out of accumulated other comprehensive income (loss)
Total amounts reclassified out of AOCI, pretax	114	(85)
Total tax effect	(44)	29
Total amounts reclassified out of AOCI, after-tax	$ 70	$ (56)

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

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