Discontinued Operations and Assets Held For Sale - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($) Property	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties held for sale | Property	2
Number of properties sold previously held for sale | Property	2
(Loss) gains from dispositions of real estate	$ (205,000)	$ 339,000	$ 8,995,000
Gain from sale of properties	$ 2,373,000
Number of properties sold | Property	12
Number of properties for which gains on dispositions are included in earnings | Property	12
Ramoco Affiliates [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on property condemnations	$ 177,000
Deferred gain on sale of property	3,868,000
Properties Previously Classified Held for Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
(Loss) gains from dispositions of real estate	$ (205,000)