Investments in Unconsolidated Entities and International Investments - Combined Balance Sheets (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Our Share of:
Investment in Klepierre, at equity	$ 1,718,402	$ 1,769,488
Unconsolidated properties | Maximum
Our Share of:
Estimated life of investment property	40 years
Equity Method Investees excluding Klepierre, Aeropostale, ABG and HBS | Unconsolidated properties
Assets:
Investment properties, at cost	$ 19,124,164	18,807,449
Less - accumulated depreciation	7,119,224	6,834,633
Investment properties at cost, net	12,004,940	11,972,816
Cash and cash equivalents	882,158	1,076,398
Tenant receivables and accrued revenue, net	425,658	445,148
Deferred costs and other assets	618,538	390,818
Total assets	13,931,294	13,885,180
Liabilities and Partners' Deficit:
Mortgages	15,253,009	15,235,415
Accounts payable, accrued expenses, intangibles, and deferred revenue	881,032	976,311
Other liabilities	554,459	344,205
Total liabilities	16,688,500	16,555,931
Preferred units	67,450	67,450
Partners' deficit	(2,824,656)	(2,738,201)
Total liabilities and partners' deficit	13,931,294	13,885,180
Our Share of:
Partners' deficit	(1,227,185)	(1,168,216)
Add: Excess Investment	1,564,970	1,594,198
Investment in Klepierre, at equity	$ 337,785	$ 425,982