Lease Incentives (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($) property	Dec. 31, 2017 USD ($)
Lease Incentives
Non-contingent lease incentives	$ 15,069		$ 14,904
Contingent lease incentives	6,338		6,577
Total	21,407		$ 21,481
Non-contingent lease incentives, funding	1,017	$ 5,172
Total funding	1,017	5,172
Non-contingent lease incentives, Amortization	(852)	(777)
Contingent lease incentives, Amortization	(239)	(334)
Total amortization	$ (1,091)	(1,111)
Non-contingent lease incentives, Write off		(1,205)
Total Write off		$ (1,205)
Number of properties with lease incentives write-offs | property		2