MORTGAGE LOANS - Delinquent Loans (Details) - Commercial mortgage loans $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019 USD ($) loan	Dec. 31, 2018 USD ($) loan
Delinquent loans
Commercial mortgage loans | $	$ 2,371	$ 2,278
Number of delinquent commercial mortgage loans | loan	5	5
30-59 Days Delinquent
Delinquent loans
Commercial mortgage loans | $	$ 1,641	$ 1,044
Number of delinquent commercial mortgage loans | loan	2	4
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 | $	$ 730	$ 1,234
Number of delinquent commercial mortgage loans | loan	3	1