CHANGES IN ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Change in accumulated other comprehensive income (loss), pretax
Balance at the beginning of the period, pretax	$ (25,645)		$ (28,846)		$ (27,596)		$ (25,334)
Change in net unrealized gains (losses) on investment securities, pretax	(321)		(20)		1,967		(3,013)
Cash flow hedges, pretax	45		514		431		1,519
Benefit plans, pretax	107		326		(187)		1,323
Foreign currency translation adjustment, pretax	(2,094)		338		(2,523)		(2,183)
Change, pretax	(2,263)		1,158		(312)		(2,354)
Balance at the end of the period, pretax	(27,908)		(27,688)		(27,908)		(27,688)
Change in accumulated other comprehensive income (loss), tax effect
Balance at the beginning of the period, tax effect	7,498		8,922		8,463		8,438
Change in net unrealized gains (losses) on investment securities, tax effect	114		12		(740)		1,107
Cash flow hedges, tax effect	(17)		(184)		(165)		(567)
Benefit plans, tax effect	(36)		(28)		81		(370)
Foreign currency translation adjustment, tax effect	373		168		293		282
Change, tax effect	434		(32)		(531)		452
Balance at the end of the period, tax effect	7,932		8,890		7,932		8,890
Change in accumulated other comprehensive income (loss), after-tax
Beginning-of-period balance, net of tax	(18,147)		(19,924)		(19,133)		(16,896)
Change in net unrealized gains (losses) on investment securities, after-tax	(207)		(8)		1,227		(1,906)
Cash flow hedges, after-tax	28		330		266		952
Benefit plans, after-tax	71	[1]	298	[1]	(106)	[1]	953	[1]
Foreign currency translation adjustment, after-tax	(1,721)		506		(2,230)		(1,901)
Citigroup’s total other comprehensive income (loss)	(1,829)		1,126		(843)		(1,902)
End-of-period balance, net of tax	$ (19,976)		$ (18,798)		$ (19,976)		$ (18,798)

[1] Primarily reflects adjustments based on the quarterly actuarial valuations of the Company’s significant pension and postretirement plans and amortization of amounts previously recognized in Other comprehensive income.