CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Properties held-for-sale, accumulated depreciation	$ 1,916	$ 1,916
Mortgage loans receivable, loan loss reserve	2,355	2,255
Notes receivable, loan loss reserve	142	166
Straight-line rent receivable, allowance for doubtful accounts	$ 707	$ 814
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	60,000	60,000
Common stock, shares issued	39,635	39,570
Common stock, shares outstanding	39,635	39,570
Senior Unsecured Notes
Debt issue costs, net	$ 1,027	$ 1,131