Impairment Charges and Impairment of Joint Venture Investments - Impairment Charges on Assets or Investments (Parenthetical) (Detail)	3 Months Ended
	Mar. 31, 2015 ShoppingCenter	Sep. 30, 2015 Land
Operating Shopping Centers [Member]
Schedule Of Investments [Line Items]
Number of properties | ShoppingCenter	25
Land Parcels [Member]
Schedule Of Investments [Line Items]
Number of properties		5
Minimum [Member]
Schedule Of Investments [Line Items]
Asset disposal period	12 months
Maximum [Member]
Schedule Of Investments [Line Items]
Asset disposal period	24 months