DISCONTINUED OPERATIONS AND SIGNIFICANT DISPOSALS - Significant Disposals (Details) loan in Thousands, $ in Millions			3 Months Ended				9 Months Ended
		Jan. 01, 2016	Sep. 30, 2017 USD ($)	Mar. 31, 2017 USD ($) employee branch loan	Sep. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Aug. 31, 2017 USD ($)
Discontinued operations
Pre-tax gain (loss) on sale	[1]						$ 602	$ 422
Disposed of by sale, not discontinued operations | Novation of 80% Primerica Coinsurance Agreement
Discontinued operations
Coinsurance agreement percentage		80.00%
Pre-tax gain (loss) on sale						$ 404
After tax gain (loss) on sale of disposal group						263
AFS securities and cash						1,500
Deferred policy acquisition costs						950
Liabilities						$ 2,700
Disposed of by sale, not discontinued operations | US Mortgage Servicing Operations
Discontinued operations
Pre-tax gain (loss) on sale				$ (331)
After tax gain (loss) on sale of disposal group				(207)
Loss on disposal including other costs relating to disposal				382
Servicing related assets				1,162
Mortgage servicing rights				$ 1,046
Number of loans disposed of | loan				750
Loans, net				$ 93,000
Disposed of by sale, not discontinued operations | CitiFinancial Canada
Discontinued operations
Pre-tax gain (loss) on sale				350
After tax gain (loss) on sale of disposal group				178
Liabilities				1,500
Loans, net				$ 1,700
Number of branches | branch				220
Number of employees | employee				1,400
Assets				$ 1,900
Amount of debt settled				$ 400
Income before taxes			$ 0		$ 43		41	121
Disposed of by sale, not discontinued operations | Fixed Income Analytics and Index Businesses
Discontinued operations
Pre-tax gain (loss) on sale			580
After tax gain (loss) on sale of disposal group			355
Liabilities									$ 18
Assets									112
Income before taxes			$ 13		$ 12		$ 31	$ 43
Goodwill									$ 72

[1] See Note 2 to the Consolidated Financial Statements for further information on significant disposals.