Fair Value Measurements - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended		7 Months Ended	9 Months Ended			3 Months Ended	6 Months Ended	1 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended			7 Months Ended	9 Months Ended	3 Months Ended		7 Months Ended
	Jul. 31, 2014	Mar. 31, 2014	Sep. 30, 2013	Jul. 31, 2014	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Mar. 31, 2014 Jacksonville, Florida [Member]	Jun. 30, 2014 Louisville, Kentucky [Member]	Jun. 30, 2014 Marc Realty [Member]	Jun. 30, 2014 Northwest Atlanta Partners LP [Member]	Jun. 30, 2014 Sealy [Member]	Mar. 31, 2014 Minimum [Member]	Mar. 31, 2014 Maximum [Member]	Sep. 30, 2013 Fair Value, Measurements, Nonrecurring [Member]	Jul. 31, 2014 Fair Value, Measurements, Nonrecurring [Member]	Sep. 30, 2013 Fair Value, Measurements, Nonrecurring [Member]	Mar. 31, 2014 Lisle, Illinois Property Sale [Member]	Mar. 31, 2014 Greensboro, North Carolina Sale [Member]	Jul. 31, 2014 Significant Unobservable Inputs (Level 3) [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Inter-level transfer of assets	$ 0		$ 0	$ 0		$ 0
Inter-level transfer of liabilities	0		0	0		0
Loan securities carried at fair value	226,000			226,000			226,000													226,000
Loan security face value																				20.00%
Property impairment charges				9,287,000		2,904,000		200,000	87,000						2,750,000	9,287,000	2,904,000	8,500,000	500,000
Impairment charge on equity investment																2,422,000
Discount rate		8.00%									10.80%
Terminal capitalization rate											8.50%		8.50%	10.00%
Market rent growth rate		2.00%									2.70%
Expense growth rate		2.00%									2.80%
Other-than-temporary impairment charge										762,000		1,660,000
Net unrealized gain	0		0	0	73,000	73,000
Change in fair value of loan securities	$ 0		$ 0	$ 0		$ 0