INVESTMENTS - Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	[1]			$ (45)
(Addition to) release of allowance for credit losses	[2]	$ 0	$ 5	0	$ 8
Balance, end of period		(165)		(165)
Available-for-sale securities
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	[1]			0
Transition impact to retained earnings						$ 0
(Addition to) release of allowance for credit losses				(75)
Write-offs, net of recoveries				37
Balance, end of period		(38)		(38)
Transitional real estate loans
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	[1]			(22)
Transition impact to retained earnings						(2)
(Addition to) release of allowance for credit losses				(29)
Write-offs, net of recoveries				0
Balance, end of period		(53)		(53)
Commercial mortgage loans
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	[1]			(3)
Transition impact to retained earnings						(8)
(Addition to) release of allowance for credit losses				(17)
Write-offs, net of recoveries				0
Balance, end of period		(28)		(28)
Middle market loans
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	[1]			(20)
Transition impact to retained earnings						(33)
(Addition to) release of allowance for credit losses				(31)
Write-offs, net of recoveries				0
Balance, end of period		(84)		(84)
Held-to-maturity securities
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	[1]			0
Transition impact to retained earnings						(10)
(Addition to) release of allowance for credit losses				1
Write-offs, net of recoveries				0
Balance, end of period		(9)		(9)
Reinsurance recoverables
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	[1]			0
Transition impact to retained earnings						$ (11)
(Addition to) release of allowance for credit losses				0
Write-offs, net of recoveries				0
Balance, end of period		$ (11)		$ (11)

[1] U.S. GAAP guidance adopted as of January 1, 2020 has superseded these losses, included for comparative purposes only.

[2] U.S. GAAP guidance adopted as of January 1, 2020 has superseded these losses, included for comparative purposes only