DERIVATIVES - Offsetting of Financial Assets and Liabilities and Derivative Instruments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019
Securities Sold under Agreements to Repurchase
Net Amount Presented in the Balance Sheets	$ 573	$ 0
Interest expense, securities sold under agreements to repurchase	2
Total derivatives
Assets
Gross Amount Recognized	2,946	5,804
Gross Amount Offset in the Balance Sheets	2,912	5,429
Net Amount Presented in the Balance Sheets	34	375
Gross Amount not Offset in the Balance Sheets	0	(77)
Net Amount	34	298
Liabilities
Gross Amount Recognized	3,109	5,474
Gross Amount Offset in the Balance Sheets	2,912	5,429
Net Amount Presented in the Balance Sheets	197	45
Gross Amount not Offset in the Balance Sheets	0	0
Net Amount	197	45
Other financial instruments
Assets
Gross Amount Recognized	1,520	1,754
Gross Amount Offset in the Balance Sheets	0	0
Net Amount Presented in the Balance Sheets	1,520	1,754
Gross Amount not Offset in the Balance Sheets	0	0
Net Amount	1,520	1,754
Other invested assets
Assets
Gross Amount Recognized	4,466	7,558
Gross Amount Offset in the Balance Sheets	2,912	5,429
Net Amount Presented in the Balance Sheets	1,554	2,129
Gross Amount not Offset in the Balance Sheets	0	(77)
Net Amount	1,554	2,052
Other financial liabilities
Liabilities
Gross Amount Recognized	1,263	1,723
Gross Amount Offset in the Balance Sheets	0	0
Net Amount Presented in the Balance Sheets	1,263	1,723
Gross Amount not Offset in the Balance Sheets	0	0
Net Amount	1,263	1,723
Other liabilities
Liabilities
Gross Amount Recognized	4,372	7,197
Gross Amount Offset in the Balance Sheets	2,912	5,429
Net Amount Presented in the Balance Sheets	1,460	1,768
Gross Amount not Offset in the Balance Sheets	0	0
Net Amount	1,460	$ 1,768
Securities sold under agreement to repurchase
Securities Sold under Agreements to Repurchase
Gross Amount Recognized	571
Gross Amount Offset in the Balance Sheets	0
Net Amount Presented in the Balance Sheets	571
Gross Amount not Offset in the Balance Sheets	(588)
Net Amount	$ (17)