INVESTMENTS (Details 8) (USD $) In Millions	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
OTTI on Investments disclosures
Total OTTI losses recognized during the period	$ 137		$ 445
Less: portion of OTTI loss recognized in AOCI (before taxes)	2	10	47	56
Net impairment losses recognized in earnings for securities that the Company does not intend to sell nor will likely be required to sell	135		398
OTTI losses recognized in earnings for securities that the Company intends to sell or more- likely-than-not will be required to sell before recovery	11		1,626
Total impairment losses recognized in earnings	146		2,024
Total securities AFS
OTTI on Investments disclosures
Total OTTI losses recognized during the period	4		72
Less: portion of OTTI loss recognized in AOCI (before taxes)	2		47
Net impairment losses recognized in earnings for securities that the Company does not intend to sell nor will likely be required to sell	2		25
OTTI losses recognized in earnings for securities that the Company intends to sell or more- likely-than-not will be required to sell before recovery	11		239
Total impairment losses recognized in earnings	13		264
Held-to-maturity Securities.
OTTI on Investments disclosures
Total OTTI losses recognized during the period	133		373
Net impairment losses recognized in earnings for securities that the Company does not intend to sell nor will likely be required to sell	133		373
OTTI losses recognized in earnings for securities that the Company intends to sell or more- likely-than-not will be required to sell before recovery			1,387
Total impairment losses recognized in earnings	$ 133		$ 1,760

Name:	c_ImpairmentLossesRelatedToSecuritiesAbstract
Namespace Prefix:	c
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

For investments that the entity does not intend to sell nor will likely be required to sell, the amount which the fair value of an investment is less than the amortized cost basis or carrying amount at the balance sheet date and the decline in fair value is deemed to be other than temporary, net of amount recognized in other comprehensive income.

+ Details

Name:	c_OtherComprehensiveIncomeReclassificationBeforeTax
Namespace Prefix:	c
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

For investments that the entity does not intend to sell nor will likely be required to sell, the amount by which the fair value of an investment is less than the amortized cost basis or carrying amount at the balance sheet date and the decline in fair value is deemed to be other than temporary, net of amount recognized in other comprehensive income.

+ Details

Name:	c_OtherThanTemporaryImpairmentLossesInvestmentsNotBeingSoldPortionRecognizedInEarningsNet
Namespace Prefix:	c
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

For investments, the amount by which the fair value of an investment is less than the amortized cost basis or carrying amount at the balance sheet date and the decline in fair value is deemed to be other than temporary, net of amount recognized in other comprehensive income.

+ Details

Name:	c_OtherThanTemporaryImpairmentLossesInvestmentsRecognizedInEarningsNet
Namespace Prefix:	c
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

For investments that the entity does not intend to sell nor will likely be required to sell, the amount by which the fair value of an investment is less than the amortized cost basis or carrying amount at the balance sheet date and the decline in fair value is deemed to be other than temporary, prior to considering whether or not such amount is recognized in earnings or other comprehensive income.

+ Details

Name:	c_OtherThanTemporaryImpairmentLossesInvestmentsWithIntentNotToSell
Namespace Prefix:	c
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

For investments that the entity does intend to sell or will more-likely-than-not be required to sell before recovery, the amount by which the fair value of an investment is less than the amortized cost basis or carrying amount at the balance sheet date and the decline in fair value is deemed to be other than temporary.

+ Details

Name:	c_OtherThanTemporaryImpairmentLossesInvestmentsWithIntentToSell
Namespace Prefix:	c
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration