Debt - Mortgage Loans Payable (Parenthetical) (Detail) - Mortgage Loans Payable [Member]	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
LIBOR rate	0.193%	0.17125%
Phoenix Az [Member]
Debt Instrument [Line Items]
Percentage of proceeds from sale of property used to repay mortgage	100.00%
3.50% Loan Due in May 2016 [Member]
Debt Instrument [Line Items]
Debt instrument basis spread on floor rate	1.00%
2.69% Loan Due in Oct 2016 [Member]
Debt Instrument [Line Items]
Mortgage loan, LIBOR rate	0.69%