CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Rental and other property revenues	$ 125,233	$ 118,471	$ 102,220
Property operating expenses	63,056	61,918	52,257
General and administrative	6,269	5,476	5,508
Interest income	13,862	14,670	10,687
Mortgage and loan interest	59,944	53,088	46,541
Recognition of deferred gains	9,842	0	0
Related Parties [Member]
Rental and other property revenues	839	708	726
Property operating expenses	929	865	740
General and administrative	3,120	3,574	3,105
Interest income	11,485	13,348	10,071
Mortgage and loan interest	$ 0	$ 568	$ 0