Acquisitions and Dispositions (Dispositions) (Details) $ in Thousands	1 Months Ended						3 Months Ended						9 Months Ended
	Aug. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	May 31, 2017 USD ($)	Apr. 30, 2017 USD ($) loan	Mar. 31, 2017 USD ($)	Jan. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2017 USD ($) outparcel	Sep. 30, 2016 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Price, Gross													$ 189,750
Sales Price, Net													112,076
Gain (loss)													(75,980)
Loss on impairment							$ 24,935		$ 53,558				71,401	$ 116,736
Gain on sales of real estate assets													86,904	14,503
Gain on extinguishment of debt							6,452		(6)				30,927	$ 0
Outparcel Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sales of real estate assets													$ 10,924
Number of properties disposed of (outparcel) | outparcel													8
Malls
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on impairment					$ 3,147
College Square | Malls
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss)							$ 1,448	$ (1,994)
One and Two Oyster Point
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Price, Gross						$ 6,250
Sales Price, Net						6,142
Gain (loss)						0
Loss on impairment									$ 3,844
Outlet Shoppes at Oklahoma City
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Price, Gross				$ 130,000
Sales Price, Net				55,368
Gain (loss)				$ (75,434)
Number of loans retired (loan) | loan				3
Priority received				$ 7,477
Outlet Shoppes at Oklahoma City | Corporate Joint Venture
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of equity interest in real estate property				2500.00%
Outlet Shoppes at Oklahoma City | Parent Company
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss)				$ (48,800)
Percentage of equity interest in real estate property				7500.00%
College Square Mall and Foothills Mall
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales Price, Gross			$ 53,500
Sales Price, Net			50,566
Gain (loss)			$ (546)
Midland Mall
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on impairment											$ 4,681
Balance of Non-recourse Debt						31,953
Gain on extinguishment of debt						$ 3,760
Non-cash default interest expense											$ 479
Chesterfield Mall
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on impairment												$ 99,969
Balance of Non-recourse Debt		$ 140,000
Gain on extinguishment of debt		$ 29,187
Non-cash default interest expense												$ 4,324
Wausau Center
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on impairment										$ 10,738
Balance of Non-recourse Debt	$ 17,689
Gain on extinguishment of debt	$ 6,851
Non-cash default interest expense										$ 575
Midland Mall, Chesterfield Mall and Wausau Mall
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Balance of Non-recourse Debt													$ 189,642
Gain on extinguishment of debt													$ 39,798