Mortgages Notes Payable, Revolving Credit Facility, Interest and Amortization of Deferred Debt Costs - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Mortgage notes payable	$ 814,635,000	$ 820,068,000
Debt outstanding with fixed-rate	784,600,000	789,900,000
Debt outstanding with variable-rate	30,000,000	30,200,000
Carrying value of properties collateralizing mortgage notes	903,900,000	907,200,000
Description of variable rate basis	one-month LIBOR
Total outstanding debt		820,100,000
Van Ness Square
Debt Instrument [Line Items]
Construction-to-permanent loan	71,600,000
Northrock Loan
Debt Instrument [Line Items]
Guarantor obligations, maximum exposure	7,500,000
Fixed Rate Mortgage Notes Payable | Metro Pike Center
Debt Instrument [Line Items]
Guarantor obligations, maximum exposure, percentage	50.00%
Fixed Rate Mortgage Notes Payable | Metro Pike Center Bank Loan [Member]
Debt Instrument [Line Items]
Guarantor obligations, maximum exposure	7,800,000
Variable Rate Loans Payable [Member] | Northrock Loan
Debt Instrument [Line Items]
Amount oustanding	14,736,000
Variable Rate Loans Payable [Member] | Metro Pike Center Bank Loan [Member]
Debt Instrument [Line Items]
Amount oustanding	15,325,000
Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	175,000,000
Line of credit facility maturity date	May 20, 2016
Extension in line of credit facility period	1 year
Line of credit facility, maximum borrowing capacity	172,000,000
Interest rate spread on LIBOR	0.00%
Unsecured Revolving Credit Facility | LIBOR | Minimum
Debt Instrument [Line Items]
Interest rate spread on LIBOR	1.60%
Unsecured Revolving Credit Facility | LIBOR | Maximum
Debt Instrument [Line Items]
Interest rate spread on LIBOR	2.50%
Letter of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 628,000