Summary of Significant Accounting Policies Schedule of Variable Interest Entities (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2020 USD ($) retail_shopping_center	Dec. 31, 2019 USD ($)
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets		$ 10,936,904	$ 11,132,253
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities		4,878,757	4,842,292
Noncontrolling Interest in Variable Interest Entity		28,685	30,655
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities		6,340	17,740
Real Estate [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	[1]	127,240	325,464
Cash and Cash Equivalents [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	[1]	$ 4,496	$ 57,269
Minimum [Member]
Variable Interest Entity [Line Items]
Expected useful lives of the properties and other intangible assets		10 years
Maximum [Member]
Variable Interest Entity [Line Items]
Expected useful lives of the properties and other intangible assets		40 years
Partially Owned Properties [Member]
Variable Interest Entity [Line Items]
Number of real estate properties | retail_shopping_center		124
Consolidated Properties [Member]
Variable Interest Entity [Line Items]
Number of real estate properties | retail_shopping_center		10

[1] Included in the December 31, 2019 balances were real estate assets and cash held in Section 1031 like-kind exchanges, of which none remained at December 31, 2020.