INVESTMENTS - Commercial Mortgage Loans by Key Credit Quality Indicators (Details) - Commercial mortgage loans $ in Millions	Mar. 31, 2021 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	$ 54
2020	48
2019	652
2018	169
2017	68
Prior	749
Total Financing Receivable	$ 1,740
Weighted Average Debt Service Coverage Ratio	2.30
2021
Financing Receivable, Credit Quality Indicator [Line Items]
Weighted Average Debt Service Coverage Ratio	2.98
2020
Financing Receivable, Credit Quality Indicator [Line Items]
Weighted Average Debt Service Coverage Ratio	1.91
2019
Financing Receivable, Credit Quality Indicator [Line Items]
Weighted Average Debt Service Coverage Ratio	2.38
2018
Financing Receivable, Credit Quality Indicator [Line Items]
Weighted Average Debt Service Coverage Ratio	2.16
2017
Financing Receivable, Credit Quality Indicator [Line Items]
Weighted Average Debt Service Coverage Ratio	2.48
Prior
Financing Receivable, Credit Quality Indicator [Line Items]
Weighted Average Debt Service Coverage Ratio	2.22
Loan to Value Ratio, Zero to Fifty-nine Point Nine-nine Percent
Financing Receivable, Credit Quality Indicator [Line Items]
2021	$ 20
2020	32
2019	441
2018	129
2017	68
Prior	541
Total Financing Receivable	$ 1,231
Weighted Average Debt Service Coverage Ratio	2.46
Loan to Value Ratio, Sixty to Sixty-nine Point Nine-nine Percent
Financing Receivable, Credit Quality Indicator [Line Items]
2021	$ 34
2020	16
2019	179
2018	40
2017	0
Prior	160
Total Financing Receivable	$ 429
Weighted Average Debt Service Coverage Ratio	1.97
Loan to Value Ratio, Seventy to Seventy-nine Point Nine-nine Percent
Financing Receivable, Credit Quality Indicator [Line Items]
2021	$ 0
2020	0
2019	32
2018	0
2017	0
Prior	22
Total Financing Receivable	$ 54
Weighted Average Debt Service Coverage Ratio	1.63
Loan-to-Value Ratio Eighty Percent and Above
Financing Receivable, Credit Quality Indicator [Line Items]
2021	$ 0
2020	0
2019	0
2018	0
2017	0
Prior	26
Total Financing Receivable	$ 26
Weighted Average Debt Service Coverage Ratio	1.62

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