Debt - Mortgage Loans Payable (Parenthetical) (Detail) - Mortgage Loans Payable [Member]				6 Months Ended
	May 19, 2016	May 12, 2016	Apr. 28, 2016	Jun. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
LIBOR rate				0.46505%	0.4295%
Chicago Il [Member]
Debt Instrument [Line Items]
Date of loan repayment			Apr. 28, 2016
Greensboro, North Carolina Sale [Member]
Debt Instrument [Line Items]
Date of loan repayment		May 12, 2016
Houston, TX and Stamford, CT [Member]
Debt Instrument [Line Items]
Date of loan repayment	May 19, 2016
Percentage of proceeds from sale of property used to repay mortgage				100.00%
0% Loan Due in June 2018 [Member]
Debt Instrument [Line Items]
Mortgage loan, LIBOR rate				1.50%