Fair Value Measurements (Schedule of Impairment of Real Estate Properties) (Details) - USD ($) $ in Thousands	1 Months Ended			3 Months Ended			4 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on impairment				$ 24,935		$ 53,558		$ 71,401	$ 116,736
Fair Value	$ 81,350			81,350			$ 81,350	81,350		$ 81,350
Malls/Office Buildings
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on impairment							606
Fair Value		$ 0			$ 0
Malls
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on impairment			$ 3,147
Fair Value			0
Investment in consolidated joint venture, fair value			$ 1,000
Malls, Office Buildings
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on impairment								71,285
Fair Value	81,350			81,350			81,350	81,350		$ 81,350
Acadiana Mall | Malls
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on impairment		43,007
Fair Value		67,300			67,300
Investment in consolidated joint venture, fair value		$ 67,300			$ 67,300
Holding period					10 years
Capitalization rate					15.50%
Discount rate					15.75%
Percentage of total consolidated revenues										1.90%
Hickory Point Mall | Malls
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loss on impairment	24,525
Fair Value	$ 14,050			$ 14,050			$ 14,050	$ 14,050		$ 14,050
Holding period				10 years
Capitalization rate				18.00%
Discount rate				19.00%
Percentage of total consolidated revenues										0.50%