INVESTMENTS - Transitional Real Estate Loans by Key Credit Quality Indicators (Details) - Transitional real estate loans $ in Millions	Jun. 30, 2021 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	$ 782
2020	514
2019	2,053
2018	1,466
2017	441
Total Financing Receivable	5,256
Loan to Value Ratio, Zero to Fifty-nine Point Nine-nine Percent
Financing Receivable, Credit Quality Indicator [Line Items]
2021	419
2020	54
2019	510
2018	328
2017	77
Total Financing Receivable	1,388
Loan to Value Ratio, Sixty to Sixty-nine Point Nine-nine Percent
Financing Receivable, Credit Quality Indicator [Line Items]
2021	220
2020	171
2019	850
2018	616
2017	182
Total Financing Receivable	2,039
Loan to Value Ratio, Seventy to Seventy-nine Point Nine-nine Percent
Financing Receivable, Credit Quality Indicator [Line Items]
2021	143
2020	262
2019	693
2018	522
2017	182
Total Financing Receivable	1,802
Loan-to-Value Ratio Eighty Percent and Above
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	27
2019	0
2018	0
2017	0
Total Financing Receivable	$ 27