MORTGAGE LOANS - Impaired Loans (Details) - Commercial mortgage loans - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Recorded Investment
With no related allowance recorded, recorded investment	$ 0	$ 0
With an allowance recorded, recorded investment	5,714	0
Unpaid Principal Balance
With no related allowance recorded, unpaid principal balance	0	0
With an allowance recorded, unpaid principal balance	5,327	0
Related Allowance
With an allowance recorded, related allowance	1,481	0
Average Recorded Investment
With no related allowance recorded, average recorded investment	0	0
With an allowance recorded, average recorded investment	1,905	0
Interest Income Recognized
With no related allowance recorded, interest income recognized	0	0
With an allowance recorded, interest income recognized	197	0
Cash Basis Interest Income
With no related allowance recorded, cash basis interest income	0	0
With an allowance recorded, cash basis interest income	$ 225	$ 0

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Amount of allowance for credit losses related to recorded investment.

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Amount of average investment of impaired financing receivables for which there is no related allowance for credit losses.

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-Publisher FASB
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Amount of interest income, recognized on accrual basis, on financing receivables that are recognized as impaired, for which there is no related allowance for credit losses.

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