SCHEDULE IV MORTGAGE LOANS ON REAL ESTATE - Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Mortgage loans on real estate
Balance at the beginning of the period	$ 254,099	$ 242,939	$ 223,907
New mortgage loans		7,500	14,525
Other additions	4,253	4,842	6,839
Amortization of mortgage premium	(4)	(4)	(4)
Collections of principal	(1,065)	(1,065)	(2,136)
Loan loss reserve	(32)	(113)	(192)
Balance at the end of the period	$ 257,251	$ 254,099	$ 242,939