Debt - Mortgage Loans Payable (Parenthetical) (Detail)	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
LIBOR rate	0.152%	0.1677%
Loan interest rate description	LIBOR plus 3%
Memphis, TN [Member] | 3.00% Loan Due in Aug 2014 [Member]
Debt Instrument [Line Items]
Debt instrument basis spread on floor rate	0.50%
Debt instrument interest rate cap basis spread at LIBOR	0.50%
Loan interest rate description	LIBOR + 2.5 %
Loan interest rate	3.00%
Lisle, IL [Member] | 2.67% Loan Due in Oct 2014 [Member]
Debt Instrument [Line Items]
Debt instrument interest rate cap basis spread at LIBOR	1.00%
Loan interest rate description	LIBOR + 2.5 %
Loan interest rate	2.67%
Norridge, IL [Member]
Debt Instrument [Line Items]
Loan interest rate description	5.75% plus the greater of 0.25% or LIBOR.
Loan interest rate	5.75%
Loan interest rate additional percentage	0.25%
New York, NY [Member] | 3.50% Loan Due in May 2016 [Member]
Debt Instrument [Line Items]
Debt instrument basis spread on floor rate	1.00%
Debt instrument interest rate cap basis spread at LIBOR	1.75%
Loan interest rate description	LIBOR + 2.5 %
Loan interest rate	3.50%
Philadelphia, PA [Member] | 2.50% Loan Due in May 2016 [Member]
Debt Instrument [Line Items]
Mortgage loan, LIBOR rate	0.50%
Loan interest rate description	LIBOR + 2.0 %
Loan interest rate	2.50%
Phoenix, AZ [Member] | 2.69% Loan Due in Oct 2016 [Member]
Debt Instrument [Line Items]
Mortgage loan, LIBOR rate	0.69%
Loan interest rate description	LIBOR + 2.0 %
Loan interest rate	2.69%