Investments in Unconsolidated Entities - Combined Balance Sheets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Our Share of:
Investment in unconsolidated entities, at equity	$ 2,281,688	$ 2,266,483
Unconsolidated properties | Maximum
Our Share of:
Estimated life of investment property	40 years
Equity Method Investees excluding Klepierre, Aeropostale and HBS | Unconsolidated properties
Assets:
Investment properties, at cost	$ 18,632,287	18,328,747
Less - accumulated depreciation	6,672,267	6,371,363
Investment properties at cost, net	11,960,020	11,957,384
Cash and cash equivalents	1,013,153	956,084
Tenant receivables and accrued revenue, net	403,315	403,125
Deferred costs and other assets	395,144	355,585
Total assets	13,771,632	13,672,178
Liabilities and Partners' Deficit:
Mortgages	15,231,476	14,784,310
Accounts payable, accrued expenses, intangibles, and deferred revenues	903,599	1,033,674
Other liabilities	351,116	365,857
Total liabilities	16,486,191	16,183,841
Preferred units	67,450	67,450
Partners' deficit	(2,782,009)	(2,579,113)
Total liabilities and partners' deficit	13,771,632	13,672,178
Our Share of:
Partners' deficit	(1,204,237)	(1,144,620)
Add: Excess Investment	1,614,277	1,733,063
Investment in unconsolidated entities, at equity	$ 410,040	$ 588,443