Discontinued Operations - Additional Information (Detail) (USD $)	12 Months Ended		1 Months Ended							12 Months Ended	1 Months Ended			12 Months Ended
	Dec. 31, 2013	Dec. 31, 2011	Aug. 31, 2011 Knoxville [Member]	Dec. 31, 2011 Missouri [Member]	Jan. 31, 2011 Missouri [Member]	Mar. 31, 2013 Andover, Massachusetts Property Sale [Member] Massachusetts [Member]	Jun. 30, 2013 Arizona And Denton [Member]	Aug. 31, 2013 Seabrook [Member]	Dec. 31, 2013 701 Arboretum - Operating Property [Member]	Dec. 31, 2011 701 Arboretum - Operating Property [Member]	Sep. 30, 2012 Indiana [Member]	Jul. 31, 2013 Denton [Member]	Jun. 30, 2013 Denton [Member]	Dec. 31, 2012 Denton [Member]	Dec. 31, 2012 Memphis [Member]	Dec. 31, 2013 Meriden [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain or loss on sale of property			$ (58,000)		$ 450,000	$ 2,775,000	$ 6,745,000	$ 1,428,000	$ 58,000		$ 945,000					$ 5,106,000
Net proceeds from sale of property			2,151,000	1,485,000		11,538,000	19,585,000	3,202,000	2,351,000		1,071,000	1,703,000
Impairment charge									2,750,000	3,000,000			154,000	824,000	698,000
Settlement income	(411,000)	5,868,000													592,000
Gross sales price of property																27,500,000
Non-refundable deposit	$ 500,000															$ 500,000