Investments in and Advances to Joint Ventures - Summary of Terms For Unconsolidated Joint Ventures Investments (Detail) - BRE DDR Retail Holdings Joint Venture Acquisitions [Member] $ in Millions	9 Months Ended
	Sep. 30, 2018 USD ($) ShoppingCenter	Dec. 31, 2015 USD ($) ShoppingCenter	Oct. 31, 2014 USD ($) ShoppingCenter
BRE DDR III [Member]
Schedule Of Equity Method Investments [Line Items]
Unconsolidated Joint Venture Partner Formation Date Month And Year	2014-10
Common Equity Initial			$ 19.6
Preferred Investment (Principal)	$ 198.1		$ 300.0
Preferred Investment, Net of Reserve	$ 142.6
Properties Owned | ShoppingCenter	20		70
BRE DDR IV [Member]
Schedule Of Equity Method Investments [Line Items]
Unconsolidated Joint Venture Partner Formation Date Month And Year	2015-12
Common Equity Initial		$ 12.9
Preferred Investment (Principal)	$ 66.7	$ 82.6
Preferred Investment, Net of Reserve	$ 56.7
Properties Owned | ShoppingCenter	5	6
BRE DDR III and IV [Member]
Schedule Of Equity Method Investments [Line Items]
Preferred Investment (Principal)	$ 264.8	$ 382.6
Preferred Investment, Net of Reserve	$ 199.3