INVESTMENTS - Mortgage Loans (Details)	Sep. 30, 2023 USD ($) loan	Dec. 31, 2022 USD ($)	Sep. 30, 2022 USD ($)
Mortgage loans, held for investment:
Commercial	$ 614,456,000	$ 627,437,000
Allowance for expected credit losses	(4,179,000)	0
Total mortgage loans, held for investment	$ 610,277,000	$ 627,437,000
Commercial (as a percent)	101.00%	100.00%
Allowance for expected credit losses (as a percent)	(1.00%)	0.00%
Total mortgage loans, held-for investment (as a percent)	100.00%	100.00%
Weighted average debt service coverage ratios	1.9		2.3
Weighted average loan-to-value ratios (as a percent)	68.00%		60.00%
Commercial mortgage loans, past due amount	$ 0		$ 0
Number of collateral dependent loan | loan	2