Debt - Mortgage Loans Payable (Parenthetical) (Detail)				12 Months Ended		12 Months Ended
	Dec. 31, 2013 3.00% Loan Due in Aug 2014 [Member]	Dec. 31, 2012 3.00% Loan Due in Aug 2014 [Member]	Dec. 31, 2013 Memphis, TN [Member] 3.00% Loan Due in Aug 2014 [Member]	Dec. 31, 2013 Lisle, IL [Member] 2.68% Loan Due in Oct 2014 [Member] Property	Dec. 31, 2013 New York, NY [Member] 3.50% Loan Due in May 2016 [Member]	Dec. 31, 2013 Philadelphia PA [Member] 2.5% Loan Due in May 2016 [Member]	Dec. 31, 2013 Phoenix AZ [Member] 2.69% Loan Due in October 2014 [Member]	Dec. 31, 2013 Amherst, NY [Member]
Debt Instrument [Line Items]
LIBOR Rate	0.1677%	0.2087%
Debt instrument basis spread on floor rate			0.50%		1.00%
Debt instrument interest rate cap basis spread at LIBOR			0.50%	1.00%	1.75%
Number of properties in which loan collateralized				3
Number of properties released				2
Maturity date of loan				Oct. 30, 2012				Jul. 26, 2013
Mortgage loan, LIBOR rate						0.50%	0.69%