Investments in Unconsolidated Entities and International Investments - Combined Balance Sheets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
ASSETS:
Investment properties, at cost	$ 38,074,281	$ 37,804,495
Less - accumulated depreciation	14,692,374	13,905,776
Investment properties, at cost, net	23,381,907	23,898,719
Cash and cash equivalents	1,082,313	669,373
Tenant receivables and accrued revenue, net	1,452,295	832,151
Right-of-use assets, net	515,004	514,660
Deferred costs and other assets	1,139,041	1,214,025
Total assets	31,661,575	31,231,630
Liabilities and Partners' Deficit:
Mortgages and unsecured indebtedness	25,139,682	24,163,230
Accounts payable, accrued expenses, intangibles, and deferred revenues	1,299,062	1,390,682
Lease liabilities	517,454	516,809
Other liabilities	478,182	464,304
Total liabilities	29,458,166	28,101,319
Preferred units	187,193	219,061
Total liabilities and equity	31,661,575	31,231,630
Our Share of:
Our net Investment in unconsolidated entities, at equity	$ 1,641,680	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	$ 19,841,675	19,525,665
Less - accumulated depreciation	7,802,948	7,407,627
Investment properties, at cost, net	12,038,727	12,118,038
Cash and cash equivalents	973,669	1,015,864
Tenant receivables and accrued revenue, net	808,702	510,157
Right-of-use assets, net	181,713	185,302
Deferred costs and other assets	391,025	384,663
Total assets	14,393,836	14,214,024
Liabilities and Partners' Deficit:
Mortgages and unsecured indebtedness	15,505,554	15,391,781
Accounts payable, accrued expenses, intangibles, and deferred revenues	909,616	977,112
Lease liabilities	184,473	186,594
Other liabilities	407,147	338,412
Total liabilities	17,006,790	16,893,899
Preferred units	67,450	67,450
Partners' deficit	(2,680,404)	(2,747,325)
Total liabilities and equity	14,393,836	14,214,024
Our Share of:
Partners' deficit	(1,154,758)	(1,196,926)
Add: Excess Investment	1,414,067	1,525,903
Our net Investment in unconsolidated entities, at equity	$ 259,309	$ 328,977