Organization and Significant Accounting Policies Schedule of Variable Interest Entities (Details) $ in Thousands	Mar. 31, 2020 USD ($) retail_shopping_center	Dec. 31, 2019 USD ($)
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	$ 11,568,311	$ 11,132,253
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	5,293,076	4,842,292
Noncontrolling Interest in Variable Interest Entity	30,436	30,655
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	15,557	17,740
Real Estate [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	136,017	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	$ 4,055	$ 57,269
Partially Owned Properties [Member]
Variable Interest Entity [Line Items]
Number of real estate properties | retail_shopping_center	126
Consolidated Properties [Member]
Variable Interest Entity [Line Items]
Number of real estate properties | retail_shopping_center	11