Summary of Significant Accounting Policies - Organization and Principles of Consolidation (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) retail_shopping_center TenantAccount ShoppingCenter shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Unsecured public and private notes	$ 500,000
General Partners' Capital Account, Units Outstanding | shares	167,571,000	167,904,000
Partners' Capital Account, Units | shares	168,317,000	168,254,000
Maximum Period Of Time In Which Company Capitalizes Interest Costs	12 months
Tax Basis of Investments, Unrealized Appreciation (Depreciation), Net	$ 2,800,000	$ 2,800,000
Restricted Cash and Cash Equivalents	$ 2,542	2,658
Cash and cash equivalents and restricted original maturity	90 days or less
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	$ 0	0	$ 9,737
Concentration risk, percentage	23.00%
Number of tenant | TenantAccount	0
Number of shopping center. | ShoppingCenter	0
Parent Company [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Restricted Cash and Cash Equivalents	$ 2,500	$ 2,700
Maximum [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Concentration risk, percentage	5.00%
Land Improvements [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property, Plant and Equipment, Useful Life	15 years
Building and Improvements [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property, Plant and Equipment, Useful Life	40 years
Tenant Improvements [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Furniture and Equipment [Member] | Minimum [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Furniture and Equipment [Member] | Maximum [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Property, Plant and Equipment, Useful Life	7 years
Operating Partnership [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Ownership percentage of outstanding common partnership units	99.60%
General Partners' Capital Account, Units Outstanding | shares	167,571,218
Parent Company, Ownership Percentage of Outstanding Common Partnership Units of Operating Partnership	99.60%	99.60%
Wholly Owned Properties [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of real estate properties | retail_shopping_center	303
Unconsolidated Properties [Member]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of real estate properties | retail_shopping_center	116