INSURANCE LIABILITIES - Rollforward of Liability and Reinsurance Ceded (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
GMDB Direct
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Opening Balance	$ 5,052	$ 4,670	$ 4,784	$ 4,659
Paid guarantee benefits	(111)	(118)
Other changes in reserves	379	129
Closing Balance	5,052	4,670	4,784	4,659
GMDB Assumed
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Opening Balance	72	77	76	82
Paid guarantee benefits	(6)	(6)
Other changes in reserves	2	1
Closing Balance	72	77	76	82
GMDB
Guaranteed Minimum Death Benefit Reinsurance Ceded [Roll Forward]
Opening Balance	(105)	(113)
Paid guarantee benefits	5	4
Other changes in reserve	(11)	0
Ending Balance	(111)	(109)
GMIB Direct
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Opening Balance	6,299	3,742	4,691	3,743
Paid guarantee benefits	(74)	(56)
Other changes in reserves	1,682	55
Closing Balance	6,299	3,742	4,691	3,743
GMIB Assumed
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Opening Balance	219	182	187	184
Paid guarantee benefits	(1)	(1)
Other changes in reserves	33	(1)
Closing Balance	219	182	$ 187	$ 184
GMIB Ceded
Guaranteed Minimum Death Benefit Reinsurance Ceded [Roll Forward]
Opening Balance	(2,139)	(1,732)
Paid guarantee benefits	20	21
Other changes in reserve	(704)	(29)
Ending Balance	$ (2,823)	$ (1,740)