Debt - Mortgage Loans Payable (Parenthetical) (Detail)							6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014 Memphis, TN [Member] 3.00% Loan Due in Aug 2014 [Member]	Jun. 30, 2014 Lisle, IL [Member] 2.69% Loan Due in Oct 2014 [Member]	Jun. 30, 2014 Norridge, IL [Member] 6% Loan Due in Apr 2015 [Member]	Jun. 30, 2014 New York, NY [Member] 3.50% Loan Due in May 2016 [Member]	Jun. 30, 2014 Philadelphia, PA [Member] 2.50% Loan Due in May 2016 [Member]	Jun. 30, 2014 Phoenix, AZ [Member] 2.69% Loan Due in Oct 2016 [Member]
Debt Instrument [Line Items]
LIBOR rate	0.1552%	0.1677%
Debt instrument basis spread on floor rate			0.50%		0.25%	1.00%
Debt instrument interest rate cap basis spread at LIBOR			0.50%	1.00%
Mortgage loan, LIBOR rate							0.50%	0.69%