INVESTMENTS - Schedule of Allowance for Credit Losses for AFS Debt Securities (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period		$ 5	$ 0	$ 5	$ 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	8	0	8
Net reserve builds (releases) on securities with previous credit losses		0	0	0	0
Total provision for credit losses	[1]	0	8	0	8
Initial allowance on newly purchased credit-deteriorated securities during the period		0	0	0	0
Allowance for credit losses at end of period		5	8	5	8
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	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	3	0	3
Net reserve builds (releases) on securities with previous credit losses		0	0	0	0
Total provision for credit losses		0	3	0	3
Initial allowance on newly purchased credit-deteriorated securities during the period		0	0	0	0
Allowance for credit losses at end of period		0	3	0	3
Corporate
Debt Securities, Available-for-sale, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses at beginning of period		5	0	5	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	5	0	5
Net reserve builds (releases) on securities with previous credit losses		0	0	0	0
Total provision for credit losses		0	5	0	5
Initial allowance on newly purchased credit-deteriorated securities during the period		0	0	0	0
Allowance for credit losses at end of period		$ 5	$ 5	$ 5	$ 5

[1] In accordance with ASC 326.