INVESTMENTS - DERIVATIVES OFFSETTING FINANCIAL LIABILITIES (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Securities sold under agreement to repurchase
Net Amounts Presented in the Balance Sheets	$ 1,904	$ 1,887
Expense in securities sold under agreement to repurchase	13,446	14,228
Equity contracts
Offsetting Liabilities [Line Items]
Gross Amounts Recognized	1,406	1,555
Gross Amounts Offset in the Balance Sheets	1,406	1,555
Net Amounts Presented in the Balance Sheets	0	0
Interest rate contracts
Offsetting Liabilities [Line Items]
Gross Amounts Recognized	347	191
Gross Amounts Offset in the Balance Sheets	347	191
Net Amounts Presented in the Balance Sheets	0	0
Credit contracts
Offsetting Liabilities [Line Items]
Gross Amounts Recognized	3	3
Gross Amounts Offset in the Balance Sheets	3	3
Net Amounts Presented in the Balance Sheets	0	0
Currency
Offsetting Liabilities [Line Items]
Gross Amounts Recognized	52	10
Gross Amounts Offset in the Balance Sheets	52	10
Net Amounts Presented in the Balance Sheets	0	0
Margin
Offsetting Liabilities [Line Items]
Gross Amounts Recognized	0	0
Gross Amounts Offset in the Balance Sheets	0	0
Net Amounts Presented in the Balance Sheets	0	0
Securities sold under agreement to repurchase
Expense in securities sold under agreement to repurchase	16	24
Collateral
Offsetting Liabilities [Line Items]
Gross Amounts Recognized	1,824	1,855
Gross Amounts Offset in the Balance Sheets	1,824	1,855
Net Amounts Presented in the Balance Sheets	0	0
Securities sold under agreement to repurchase
Expense in securities sold under agreement to repurchase	8	4
Total Derivatives, subject to an ISDA Master Agreement
Offsetting Liabilities [Line Items]
Gross Amounts Recognized	3,632	3,614
Gross Amounts Offset in the Balance Sheets	3,632	3,614
Net Amounts Presented in the Balance Sheets	0	0
Total Derivatives, not subject to an ISDA Master Agreement
Offsetting Liabilities [Line Items]
Gross Amounts Recognized	0	0
Gross Amounts Offset in the Balance Sheets	0	0
Net Amounts Presented in the Balance Sheets	0	0
Total Derivatives
Offsetting Liabilities [Line Items]
Gross Amounts Recognized	3,632	3,614
Gross Amounts Offset in the Balance Sheets	3,632	3,614
Net Amounts Presented in the Balance Sheets	0	0
Other financial liabilities
Offsetting Liabilities [Line Items]
Gross Amounts Recognized	3,041	2,663
Gross Amounts Offset in the Balance Sheets	0	0
Net Amounts Presented in the Balance Sheets	3,041	2,663
Other liabilities
Offsetting Liabilities [Line Items]
Gross Amounts Recognized	6,673	6,277
Gross Amounts Offset in the Balance Sheets	3,632	3,614
Net Amounts Presented in the Balance Sheets	3,041	2,663
Securities sold under agreement to repurchase
Securities sold under agreement to repurchase
Gross Amounts Recognized	1,897	1,882
Gross Amounts Offset in the Balance Sheets	0	0
Net Amounts Presented in the Balance Sheets	$ 1,897	$ 1,882