COMMERCIAL MORTGAGE LOANS - Impaired Loans (Details) - Commercial mortgage loans - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Recorded Investment
With no related allowance recorded, recorded investment	$ 848	$ 710
With an allowance recorded, recorded investment	0	16,209
Unpaid Principal Balance
With no related allowance recorded, unpaid principal balance	801	702
With an allowance recorded, unpaid principal balance	0	16,102
Related Allowance
With an allowance recorded, related allowance	0	4,884
Average Recorded Investment
With no related allowance recorded, average recorded investment	848	237
With an allowance recorded, average recorded investment	0	3,242
Interest Income Recognized
With no related allowance recorded, interest income recognized	33	20
With an allowance recorded, interest income recognized	0	841
Cash Basis Interest Income
With no related allowance recorded, cash basis interest income	37	28
With an allowance recorded, recorded investment	$ 0	$ 838

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