FAIR VALUE DISCLOSURES - Fair Value Measurement Reconciliation for All Levels (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Total gains (losses), realized and unrealized, included in:
Investment gains (losses), net	$ 65	$ (11)
Transfers into level 3	0	17
Transfers into level 3	(126)	(69)
Corporate
Total gains (losses), realized and unrealized, included in:
OCI	(61)	9
Corporate | Level 3
Total gains (losses), realized and unrealized, included in:
Beginning Balance	1,257	1,186	$ 1,186
Net investment income (loss)	1	1
Investment gains (losses), net	(2)	0
Total realized and unrealized gains (losses)	(1)	1
OCI	(61)	9
Purchases	61	70
Actual return on plan assets — Sales/Settlements	(45)	(34)
Transfers into level 3	0	17
Transfers into level 3	(26)	(69)
Ending Balance	1,185	1,180	1,257
States and political subdivisions
Total gains (losses), realized and unrealized, included in:
OCI	(2)	1
States and political subdivisions | Level 3
Total gains (losses), realized and unrealized, included in:
Beginning Balance	39	39	39
Net investment income (loss)	0	0
Investment gains (losses), net	0	0
Total realized and unrealized gains (losses)	0	0
OCI	(3)	1
Purchases	0	0
Actual return on plan assets — Sales/Settlements	0	0
Transfers into level 3	0	0
Transfers into level 3	0	0
Ending Balance	36	40	39
Asset-backed
Total gains (losses), realized and unrealized, included in:
OCI	(8)	4
Asset-backed | Level 3
Total gains (losses), realized and unrealized, included in:
Beginning Balance	100	519	519
Net investment income (loss)	0	0
Investment gains (losses), net	0	0
Total realized and unrealized gains (losses)	0	0
OCI	(8)	4
Purchases	48	11
Actual return on plan assets — Sales/Settlements	0	0
Transfers into level 3	0	0
Transfers into level 3	(100)	0
Ending Balance	40	534	100
Other equity investments | Level 3
Total gains (losses), realized and unrealized, included in:
Beginning Balance	150	165	165
Investment gains (losses), net	7	0
Net derivative gains (losses), excluding non-performance risk	0	0
Nonperformance risk	0	0
Total realized and unrealized gains (losses)	7	0
OCI	(7)	0
Purchases	2	2
Actual return on plan assets — Sales/Settlements	(11)	0
Settlements	0	0
Change in estimate	0	0
Activity related to consolidated VIEs/VOEs	(1)	(1)
Transfers into level 3	0	0
Transfers into level 3	0	(29)
Ending Balance	140	137	150
GMIB Reinsurance Contract Asset
Total gains (losses), realized and unrealized, included in:
OCI	0	0
GMIB Reinsurance Contract Asset | Level 3
Total gains (losses), realized and unrealized, included in:
Beginning Balance	2,139	1,732	1,732
Investment gains (losses), net	0	0
Net derivative gains (losses), excluding non-performance risk	955	(11)
Nonperformance risk	(229)	29
Total realized and unrealized gains (losses)	726	18
OCI	0	0
Purchases	10	11
Actual return on plan assets — Sales/Settlements	(20)	(21)
Settlements	0	0
Change in estimate	(32)	0
Activity related to consolidated VIEs/VOEs	0	0
Transfers into level 3	0	0
Transfers into level 3	0	0
Ending Balance	2,823	1,740	2,139
Separate Accounts Assets | Level 3
Total gains (losses), realized and unrealized, included in:
Beginning Balance	0	21	21
Investment gains (losses), net	0	0
Net derivative gains (losses), excluding non-performance risk	0	0
Nonperformance risk	0	0
Total realized and unrealized gains (losses)	0	0
OCI	0	0
Purchases	0	4
Actual return on plan assets — Sales/Settlements	0	0
Settlements	0	(1)
Change in estimate	0	0
Activity related to consolidated VIEs/VOEs	0	0
Transfers into level 3	0	0
Transfers into level 3	0	(1)
Ending Balance	0	23	0
GMxB Derivative Features Liability | Level 3
Total gains (losses), realized and unrealized, included in:
Beginning Balance	(8,432)	(5,614)	(5,614)
Investment gains (losses), net	0	0
Net derivative gains (losses), excluding non-performance risk	(3,884)	63
Nonperformance risk	2,686	(470)
Total realized and unrealized gains (losses)	(1,198)	(407)
OCI	0	0
Purchases	(111)	(111)
Actual return on plan assets — Sales/Settlements	14	6
Settlements	0	0
Change in estimate	0	0
Activity related to consolidated VIEs/VOEs	0	0
Transfers into level 3	0	0
Transfers into level 3	0	0
Ending Balance	(9,727)	(6,126)	(8,432)
Contingent Payment Arrangement | Level 3
Total gains (losses), realized and unrealized, included in:
Beginning Balance	(23)	(7)	(7)
Investment gains (losses), net	0	0
Net derivative gains (losses), excluding non-performance risk	0	0
Nonperformance risk	0	0
Total realized and unrealized gains (losses)	0	0
OCI	0	0
Purchases	0	0
Actual return on plan assets — Sales/Settlements	0	0
Settlements	0	0
Change in estimate	0	0
Activity related to consolidated VIEs/VOEs	(1)	0
Transfers into level 3	0	0
Transfers into level 3	0	0
Ending Balance	$ (24)	$ (7)	$ (23)