SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation and qualifying accounts
Balance at beginning of period	$ 3,441	$ 3,023	$ 2,404
(Recovered) charged to costs and expenses	(206)	457	619
Deductions		(39)
Balance at end of period	3,235	3,441	3,023
Loan loss reserves
Valuation and qualifying accounts
Balance at beginning of period	2,315	2,190	1,673
(Recovered) charged to costs and expenses	(60)	125	517
Balance at end of period	2,255	2,315	2,190
Other notes receivable allowance
Valuation and qualifying accounts
Balance at beginning of period	166
(Recovered) charged to costs and expenses		166
Balance at end of period	166	166
Straight-line rent receivable allowance
Valuation and qualifying accounts
Balance at beginning of period	960	833	731
(Recovered) charged to costs and expenses	(146)	166	102
Deductions		(39)
Balance at end of period	$ 814	$ 960	$ 833