INVESTMENTS - Allowance for Loan Losses by Portfolio Segment (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($)
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	$ (180)
Balance, end of period	(154)
Transitional real estate loans
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	(63)
(Addition to) release of allowance for credit losses	16
Write-offs, net of recoveries	0
Balance, end of period	(47)
Commercial mortgage loans
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	(33)
(Addition to) release of allowance for credit losses	9
Write-offs, net of recoveries	0
Balance, end of period	(24)
Middle market loans
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	(85)
(Addition to) release of allowance for credit losses	2
Write-offs, net of recoveries	0
Balance, end of period	(83)
Held-to-maturity securities
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	(9)
(Addition to) release of allowance for credit losses	1
Write-offs, net of recoveries	0
Balance, end of period	(8)
Available-for-sale securities
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	(38)
(Addition to) release of allowance for credit losses	0
Write-offs, net of recoveries	11
Balance, end of period	(27)
Reinsurance recoverables
Allowance for Loan Losses by Portfolio Segment [Roll Forward]
Balance, beginning of period	(11)
(Addition to) release of allowance for credit losses	(2)
Write-offs, net of recoveries	0
Balance, end of period	$ (13)