INVESTMENTS - Middle Market Loans by Key Credit Quality Indicators (Details) - Middle market loans $ in Millions	Mar. 31, 2021 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	$ 149
2020	1,039
2019	1,155
2018	751
2017	477
Prior	266
Revolving Loans	417
Total Financing Receivable	4,254
BBB Credit Rating
Financing Receivable, Credit Quality Indicator [Line Items]
2021	7
2020	70
2019	73
2018	30
2017	10
Prior	4
Revolving Loans	44
Total Financing Receivable	238
BB Credit Rating
Financing Receivable, Credit Quality Indicator [Line Items]
2021	62
2020	387
2019	283
2018	207
2017	94
Prior	47
Revolving Loans	123
Total Financing Receivable	1,203
B Credit Rating
Financing Receivable, Credit Quality Indicator [Line Items]
2021	80
2020	569
2019	714
2018	409
2017	251
Prior	156
Revolving Loans	174
Total Financing Receivable	2,353
CCC Credit Rating
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	5
2019	85
2018	105
2017	90
Prior	59
Revolving Loans	74
Total Financing Receivable	418
CC Credit Rating
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	32
Prior	0
Revolving Loans	1
Total Financing Receivable	33
C and Lower Credit Rating
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	8
2019	0
2018	0
2017	0
Prior	0
Revolving Loans	1
Total Financing Receivable	$ 9