Discontinued Operations - Discontinued operations balance sheet components (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Land	$ 83,721	$ 87,235
Buildings and improvements	146,632	147,670
Projects under construction	6,131	1,764
Total investments in properties	236,484	236,669
Less accumulated depreciation and depletion	29,772	26,755
Net investments in properties	206,712	209,914
Accounts receivable, net	738	615
Unrealized rents	594	223
Deferred costs	942	2,708
Other assets	451	179
Assets of discontinued operations	3,194	176,694
Secured notes payable, current portion	0	125
Secured notes payable, less current portion	88,755	90,029
Accounts payable and accrued liabilities	2,829	2,081
Deferred revenue	32	107
Tenant security deposits	53	54
Liabilities of discontinued operations	1,872	32,280
Discontinued Operations, Disposed of by Sale [Member]
Land	546	40,465
Buildings and improvements	3,315	186,657
Projects under construction	0	6,617
Total investments in properties	3,861	233,739
Less accumulated depreciation and depletion	2,353	68,049
Net investments in properties	1,508	165,690
Accounts receivable, net	1,020	405
Unrealized rents	284	4,088
Deferred costs	382	6,509
Other assets	0	2
Assets of discontinued operations	3,194	176,694
Secured notes payable, current portion	0	23,825
Secured notes payable, less current portion	0	4,338
Accounts payable and accrued liabilities	249	2,289
Deferred revenue	59	967
Federal and state income taxes payable	1,527	0
Tenant security deposits	37	861
Liabilities of discontinued operations	$ 1,872	$ 32,280