Investment in Real Estate - Real Estate Held For Sale (Details)	3 Months Ended
	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) property
Real Estate [Line Items]
Number of properties held for sale | property		4
ASSETS
Investment in real estate, net	$ 8,775,000	$ 204,895,000
Accounts receivable, net	28,000	85,000
Straight-line rent receivables, net	420,000	2,234,000
Deferred leasing costs and lease intangible assets, net	2,394,000	4,063,000
Prepaid expenses and other assets, net	87,000	58,000
Assets associated with real estate held for sale	11,704,000	211,335,000
LIABILITIES
Accounts payable and accrued liabilities	393,000	782,000
Lease intangible liabilities, net	0	95,000
Security deposits and prepaid rent	237,000	1,339,000
Liabilities associated with real estate held for sale	630,000	2,216,000
Long-lived asset impairment charges	$ 0
9300 Wilshire Boulevard
Real Estate [Line Items]
Sales Price		$ 13,800,000