Investments in Unconsolidated Entities and International Investments - Combined Balance Sheets (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
ASSETS:
Investment properties, at cost	$ 37,972,093	$ 37,804,495
Less - accumulated depreciation	14,389,809	13,905,776
Investment properties, at cost, net	23,582,284	23,898,719
Cash and cash equivalents	3,306,100	669,373
Tenant receivables and accrued revenue, net	1,457,695	832,151
Right-of-use assets, net	517,061	514,660
Deferred costs and other assets	1,133,064	1,214,025
Total assets	34,026,170	31,231,630
Liabilities and Partners' Deficit:
Mortgages and unsecured indebtedness	27,268,883	24,163,230
Accounts payable, accrued expenses, intangibles, and deferred revenues	1,216,831	1,390,682
Operating lease liabilities	519,416	516,809
Other liabilities	463,380	464,304
Total liabilities	31,503,339	28,101,319
Preferred units	187,392	219,061
Total liabilities and equity	34,026,170	31,231,630
Our Share of:
Our net Investment in unconsolidated entities, at equity	$ 1,644,020	1,731,649
Unconsolidated properties | Maximum
Our Share of:
Estimated life of investment property	40 years
Equity Method Investees excluding Klepierre, ABG, HBS, RGG, Forever 21 and Sparc Group | Unconsolidated properties
ASSETS:
Investment properties, at cost	$ 19,670,435	19,525,665
Less - accumulated depreciation	7,641,911	7,407,627
Investment properties, at cost, net	12,028,524	12,118,038
Cash and cash equivalents	733,224	1,015,864
Tenant receivables and accrued revenue, net	756,871	510,157
Right-of-use assets, net	180,952	185,302
Deferred costs and other assets	368,254	384,663
Total assets	14,067,825	14,214,024
Liabilities and Partners' Deficit:
Mortgages and unsecured indebtedness	15,436,464	15,391,781
Accounts payable, accrued expenses, intangibles, and deferred revenues	808,425	977,112
Operating lease liabilities	183,406	186,594
Other liabilities	395,429	338,412
Total liabilities	16,823,724	16,893,899
Preferred units	67,450	67,450
Partners' deficit	(2,823,349)	(2,747,325)
Total liabilities and equity	14,067,825	14,214,024
Our Share of:
Partners' deficit	(1,233,667)	(1,196,926)
Add: Excess Investment	1,488,444	1,525,903
Our net Investment in unconsolidated entities, at equity	$ 254,777	$ 328,977