INVESTMENTS - Schedule of Allowance for Credit Losses for AFS Debt Securities (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period		$ 5	$ 8	$ 5	$ 0
Less: Write-offs		0	0	0	0
Recoveries of amounts written-off		0	1	0	1
Net credit losses (NCLs)		0	1	0	1
Credit losses on securities without previous credit losses		1	0	1	8
Net reserve builds (releases) on securities with previous credit losses		0	(3)	0	(3)
Total provision for credit losses	[1]	1	(4)	1	4
Initial allowance on newly purchased credit-deteriorated securities during the period		0	0	0	0
Allowance for credit losses at end of period		6	5	6	5
Mortgage-backed securities
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period		0	0	0	0
Less: Write-offs		0	0	0	0
Recoveries of amounts written-off		0	0	0	0
Net credit losses (NCLs)		0	0	0	0
Credit losses on securities without previous credit losses		0	0	0	0
Net reserve builds (releases) on securities with previous credit losses		0	0	0	0
Total provision for credit losses		0	0	0	0
Initial allowance on newly purchased credit-deteriorated securities during the period		0	0	0	0
Allowance for credit losses at end of period		0	0	0	0
U.S. Treasury and federal agency securities
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period		0	0	0	0
Less: Write-offs		0	0	0	0
Recoveries of amounts written-off		0	0	0	0
Net credit losses (NCLs)		0	0	0	0
Credit losses on securities without previous credit losses		0	0	0	0
Net reserve builds (releases) on securities with previous credit losses		0	0	0	0
Total provision for credit losses		0	0	0	0
Initial allowance on newly purchased credit-deteriorated securities during the period		0	0	0	0
Allowance for credit losses at end of period		0	0	0	0
State and municipal securities
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period		0	0	0	0
Less: Write-offs		0	0	0	0
Recoveries of amounts written-off		0	0	0	0
Net credit losses (NCLs)		0	0	0	0
Credit losses on securities without previous credit losses		0	0	0	0
Net reserve builds (releases) on securities with previous credit losses		0	0	0	0
Total provision for credit losses		0	0	0	0
Initial allowance on newly purchased credit-deteriorated securities during the period		0	0	0	0
Allowance for credit losses at end of period		0	0	0	0
Foreign government
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period		0	3	0	0
Less: Write-offs		0	0	0	0
Recoveries of amounts written-off		0	0	0	0
Net credit losses (NCLs)		0	0	0	0
Credit losses on securities without previous credit losses		0	0	0	3
Net reserve builds (releases) on securities with previous credit losses		0	(3)	0	(3)
Total provision for credit losses		0	(3)	0	0
Initial allowance on newly purchased credit-deteriorated securities during the period		0	0	0	0
Allowance for credit losses at end of period		0	0	0	0
Corporate
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period		5	5	5	0
Less: Write-offs		0	0	0	0
Recoveries of amounts written-off		0	1	0	1
Net credit losses (NCLs)		0	1	0	1
Credit losses on securities without previous credit losses		1	0	1	5
Net reserve builds (releases) on securities with previous credit losses		0	0	0	0
Total provision for credit losses		1	(1)	1	4
Initial allowance on newly purchased credit-deteriorated securities during the period		0	0	0	0
Allowance for credit losses at end of period		$ 6	$ 5	$ 6	$ 5

[1] In accordance with ASC 326.