INVESTMENTS - Transitional Real Estate Loans by Key Credit Quality Indicators (Details) - Transitional real estate loans $ in Millions	Jun. 30, 2020 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 392
2019	2,165
2018	2,227
2017	818
2016	34
Prior	57
Total Financing Receivable	5,693
Loan to Value Ratio, Zero to Fifty-nine Point Nine-nine Percent
Financing Receivable, Credit Quality Indicator [Line Items]
2020	45
2019	523
2018	417
2017	157
2016	20
Prior	57
Total Financing Receivable	1,219
Loan to Value Ratio, Sixty to Sixty-nine Point Nine-nine Percent
Financing Receivable, Credit Quality Indicator [Line Items]
2020	191
2019	790
2018	839
2017	437
2016	0
Prior	0
Total Financing Receivable	2,257
Loan to Value Ratio, Seventy to Seventy-nine Point Nine-nine Percent
Financing Receivable, Credit Quality Indicator [Line Items]
2020	131
2019	816
2018	971
2017	224
2016	14
Prior	0
Total Financing Receivable	2,156
Loan-to-Value Ratio Eighty Percent and Above
Financing Receivable, Credit Quality Indicator [Line Items]
2020	25
2019	36
2018	0
2017	0
2016	0
Prior	0
Total Financing Receivable	$ 61