INVESTMENTS - Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020		Dec. 31, 2019
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period			$ (180)
Balance, end of period	$ (165)		(165)
Transitional real estate loans
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	(41)	$ (66)	(63)	$ (22)	[1]
Cumulative Effect of Adoption of 2016-13						$ (2)
(Addition to) release of allowance for credit losses	(18)	13	4	(29)
Write-offs, net of recoveries	0	0	0	0
Balance, end of period	(59)	(53)	(59)	(53)
Commercial mortgage loans
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	(22)	(42)	(32)	(3)	[1]
Cumulative Effect of Adoption of 2016-13						(8)
(Addition to) release of allowance for credit losses	5	14	15	(17)
Write-offs, net of recoveries	0	0	0	0
Balance, end of period	(17)	(28)	(17)	(28)
Middle market loans
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	(76)	(134)	(85)	(20)	[1]
Cumulative Effect of Adoption of 2016-13						(33)
(Addition to) release of allowance for credit losses	(13)	59	(4)	(31)
Write-offs, net of recoveries	0	(9)	0	0
Balance, end of period	(89)	(84)	(89)	(84)
Held-to-maturity securities
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	(8)	(9)	(10)	0	[1]
Cumulative Effect of Adoption of 2016-13						(10)
(Addition to) release of allowance for credit losses	(1)	0	1	1
Write-offs, net of recoveries	0	0	0	0
Balance, end of period	(9)	(9)	(9)	(9)
Available-for-sale securities
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	(26)	(38)	(38)	0	[1]
Cumulative Effect of Adoption of 2016-13						0
(Addition to) release of allowance for credit losses	0	(1)	26	(75)
Write-offs, net of recoveries	26	1	12	37
Balance, end of period	0	(38)	0	(38)
Reinsurance recoverables
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	(13)	(11)	(12)	0	[1]
Cumulative Effect of Adoption of 2016-13						$ (11)
(Addition to) release of allowance for credit losses	0	0	(1)	0
Write-offs, net of recoveries	0	0	0	0
Balance, end of period	$ (13)	$ (11)	$ (13)	$ (11)

[1] U.S. GAAP guidance adopted as of January 1, 2020 has superseded these losses, included for comparative purposes only.