COMMERCIAL MORTGAGE LOANS - Delinquent Loans (Details) - Commercial Mortgage Loans $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan
Delinquent loans
Commercial mortgage loans | $	$ 0	$ 7,165
Number of delinquent commercial mortgage loans | loan	0	5
30-59 Days Delinquent
Delinquent loans
Commercial mortgage loans | $	$ 0	$ 6,455
Number of delinquent commercial mortgage loans | loan	0	2
60-89 Days Delinquent
Delinquent loans
Commercial mortgage loans | $	$ 0	$ 0
Number of delinquent commercial mortgage loans | loan	0	0
Greater than 90 Days Delinquent
Delinquent loans
Commercial mortgage loans | $	$ 0	$ 710
Number of delinquent commercial mortgage loans | loan	0	3