Subsequent Events - Additional Information (Detail) $ / shares in Units, ft² in Millions, $ in Millions	Oct. 09, 2015 USD ($) ft² $ / shares	Sep. 30, 2015 ft²	Dec. 31, 2014 ft²	Sep. 30, 2014 ft²
Subsequent Event [Line Items]
Square Feet / Acres		275.0	260.7	301.8
Subsequent Events [Member]
Subsequent Event [Line Items]
Aggregate consideration for sale | $	$ 374
Subsequent Events [Member] | Morris Realty Associates LLC [Member]
Subsequent Event [Line Items]
Units issued agreed price per unit | $ / shares	$ 43.11
Subsequent Events [Member] | Morris Realty Associates LLC [Member] | Operating Properties [Member]
Subsequent Event [Line Items]
Business acquisition purchase price allocation real estate | $	$ 820
Square Feet / Acres	3.2
Subsequent Events [Member] | Morris Realty Associates LLC [Member] | Retail Properties
Subsequent Event [Line Items]
Square Feet / Acres	2.2