Fair Value Measurements - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Financial Instruments And Fair Value Measurements [Line Items]
Inter-level transfer of assets	$ 0	$ 0
Inter-level transfer of liabilities	0	0
Loan securities carried at fair value	226,000		226,000
Property impairment charges	9,200,000
Discount rate	8.00%
Market rent growth rate	2.00%
Expense growth rate	2.00%
Net unrealized gains	0	1,718,000
Change in fair value of loan securities	0
Minimum [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Terminal capitalization rate	8.50%
Maximum [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Terminal capitalization rate	10.00%
Jacksonville, Florida [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Property impairment charges	200,000
Lisle, Illinois Property Sale [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Property impairment charges	8,500,000
Greensboro, North Carolina Sale [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Property impairment charges	500,000
Significant Unobservable Inputs (Level 3) [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Loan securities carried at fair value	226,000
Loan security face value	20.00%
Fair Value, Measurements, Nonrecurring [Member]
Financial Instruments And Fair Value Measurements [Line Items]
Valuation adjustments on fair value of assets		0
Valuation adjustments on fair value of liabilities		$ 0