Discontinued Operations - Discontinued operations balance sheet components (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Land	$ 85,072	$ 83,721
Buildings and improvements	149,505	144,543
Projects under construction	7,086	6,683
Total investments in properties	241,663	234,947
Less accumulated depreciation and depletion	29,847	28,394
Net investments in properties	211,816	206,553
Accounts receivable, net	688	564
Unrealized rents	665	53
Deferred costs	990	773
Assets of discontinued operations	3,091	3,224
Accounts payable and accrued liabilities	1,851	3,545
Deferred revenue	831	27
Tenant security deposits	244	53
Liabilities of discontinued operations	243	288
Discontinued Operations, Disposed of by Sale [Member]
Land	546	546
Buildings and improvements	3,315	3,315
Projects under construction	0	0
Total investments in properties	3,861	3,861
Less accumulated depreciation and depletion	2,396	2,374
Net investments in properties	1,465	1,487
Accounts receivable, net	811	910
Unrealized rents	488	473
Deferred costs	327	354
Assets of discontinued operations	3,091	3,224
Accounts payable and accrued liabilities	206	205
Deferred revenue	0	45
Tenant security deposits	37	38
Liabilities of discontinued operations	$ 243	$ 288