Discontinued Operations - Additional Information (Detail) (USD $)	12 Months Ended		1 Months Ended	12 Months Ended	1 Months Ended				12 Months Ended	1 Months Ended			0 Months Ended	1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Sep. 30, 2012	Dec. 31, 2012	Jun. 30, 2013	Jul. 31, 2013	Aug. 31, 2013	Dec. 31, 2013	Dec. 31, 2011	Mar. 31, 2014	May 31, 2014	Mar. 31, 2013	Jun. 25, 2014	Nov. 30, 2014	Jun. 30, 2014	Jul. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets and liabilities held for sale, land and building																$ 2,536,000
Accounts receivable																58,000
Settlement income		(411,000)
Non-refundable deposit		500,000
Notes receivable interest rate	12.78%	11.59%
Indianapolis [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain or loss on sale of property			945,000
Net proceeds from sale of property			1,071,000
Memphis [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment charge				698,000
Settlement income				592,000
Deer Valley [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain or loss on sale of property					6,745,000
Net proceeds from sale of property					19,585,000
Denton [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from sale of property						1,703,000
Impairment charge				824,000	154,000
Seabrook [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain or loss on sale of property							1,428,000
Net proceeds from sale of property							3,202,000
701 Arboretum - Operating Property [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
Net proceeds from sale of property								2,351,000
Impairment charge		2,750,000							3,000,000
Meriden [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain or loss on sale of property		4,422,000
Net proceeds from sale of property		5,106,000
Gross sales price of property		27,500,000
Non-refundable deposit		500,000
Chicago [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain or loss on sale of property										3,000
Net proceeds from sale of property										5,800,000
Cash received										1,300,000
Notes receivable										4,500,000
Notes receivable interest rate										6.00%
Crossroads [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain or loss on sale of property											5,723,000
Net proceeds from sale of property											29,633,000
Proceeds from sale of real estate, gross											31,100,000
First Anniversary [Member] | Chicago [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Notes receivable interest rate										7.00%
Second Anniversary [Member] | Chicago [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Notes receivable interest rate										8.00%
Massachusetts [Member] | Andover, Massachusetts Property Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain or loss on sale of property												2,775,000
Net proceeds from sale of property												11,538,000
Amherst [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain or loss on sale of property													946,000		946,000
Net proceeds from sale of property														2,449,000	21,226,000
Proceeds from sale of real estate, gross													23,675,000		24,500,000
Aggregate net proceeds														$ 23,675,000