Disposed Properties - Schedule of Disposal Groups (Details) $ in Thousands			12 Months Ended
	Jun. 26, 2018 USD ($)	Mar. 21, 2018 USD ($)	Dec. 31, 2019 USD ($) ft²	Dec. 31, 2018 USD ($) ft²	Dec. 31, 2017 USD ($) ft²
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gross Disposition Price			$ 357,800	$ 466,175	$ 244,066
Gain (Loss) on Extinguishment of Debt			$ (2,901)	$ 9,103	$ 840
Retail
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²			8,300,000	9,500,000	12,400,000
Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²			2,098,400	3,481,000
Gross Disposition Price			$ 357,800	$ 466,175
Gain (Loss) on Sale and Transfer of Investment Properties, net			62,011	95,097
Gain (Loss) on Extinguishment of Debt			$ (2,901)	$ 9,157
Brooks Corner | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²			173,000
Gross Disposition Price			$ 26,300
Gain (Loss) on Sale and Transfer of Investment Properties, net			5,531
Gain (Loss) on Extinguishment of Debt			$ (809)
Silverlake | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²			101,000
Gross Disposition Price			$ 6,650
Gain (Loss) on Sale and Transfer of Investment Properties, net			131
Gain (Loss) on Extinguishment of Debt			$ 0
Promenade Fultondale | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²			207,600
Gross Disposition Price			$ 23,200
Gain (Loss) on Sale and Transfer of Investment Properties, net			1,861
Gain (Loss) on Extinguishment of Debt			$ 0
Crossroads at Chesapeake Square and Chesapeake Commons | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²			198,700
Gross Disposition Price			$ 23,100
Gain (Loss) on Sale and Transfer of Investment Properties, net			1,353
Gain (Loss) on Extinguishment of Debt			$ 0
West Creek | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²			53,300
Gross Disposition Price			$ 18,700
Gain (Loss) on Sale and Transfer of Investment Properties, net			5,962
Gain (Loss) on Extinguishment of Debt			$ 0
Boynton Commons | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²			210,300
Gross Disposition Price			$ 50,000
Gain (Loss) on Sale and Transfer of Investment Properties, net			18,405
Gain (Loss) on Extinguishment of Debt			$ 0
Quebec Square | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²			207,600
Gross Disposition Price			$ 42,250
Gain (Loss) on Sale and Transfer of Investment Properties, net			(800)
Gain (Loss) on Extinguishment of Debt			$ (2,092)
Northwest Marketplace | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²			185,200
Gross Disposition Price			$ 29,500
Gain (Loss) on Sale and Transfer of Investment Properties, net			7,037
Gain (Loss) on Extinguishment of Debt			0
Northwest Marketplace | Retail | Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations, Condemnation
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				0
Gross Disposition Price				$ 0
Gain (Loss) on Sale and Transfer of Investment Properties, net			$ 248	248
Gain (Loss) on Extinguishment of Debt				$ 0
White Oak Crossing | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²			564,700
Gross Disposition Price			$ 92,500
Gain (Loss) on Sale and Transfer of Investment Properties, net			21,737
Gain (Loss) on Extinguishment of Debt			$ 0
Woodbridge Crossing | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²			197,000
Gross Disposition Price			$ 45,600
Gain (Loss) on Sale and Transfer of Investment Properties, net			794
Gain (Loss) on Extinguishment of Debt			$ 0
Sherman Town Center I & II | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				485,000
Gross Disposition Price				$ 63,000
Gain (Loss) on Sale and Transfer of Investment Properties, net				12,382
Gain (Loss) on Extinguishment of Debt				$ 0
Grafton Commons | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				239,000
Gross Disposition Price				$ 33,500
Gain (Loss) on Sale and Transfer of Investment Properties, net				6,564
Gain (Loss) on Extinguishment of Debt				$ 0
Lakeport Commons | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				283,000
Gross Disposition Price				$ 31,000
Gain (Loss) on Sale and Transfer of Investment Properties, net				(666)
Gain (Loss) on Extinguishment of Debt				$ 0
Stonecrest Marketplace | Retail | Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations, Exchange
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				265,000
Gross Disposition Price				$ 0
Gain (Loss) on Sale and Transfer of Investment Properties, net		$ 1,777		1,777
Gain (Loss) on Extinguishment of Debt				$ 10,752
Carrying value, surrendered properties		$ 23,932
Market at Morse/Hamilton | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				45,000
Gross Disposition Price				$ 10,000
Gain (Loss) on Sale and Transfer of Investment Properties, net				1,592
Gain (Loss) on Extinguishment of Debt				$ 0
Siegen Plaza | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				156,000
Gross Disposition Price				$ 29,000
Gain (Loss) on Sale and Transfer of Investment Properties, net				3,849
Gain (Loss) on Extinguishment of Debt				$ (54)
Tomball Town Center | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				67,000
Gross Disposition Price				$ 22,750
Gain (Loss) on Sale and Transfer of Investment Properties, net				7,184
Gain (Loss) on Extinguishment of Debt				$ 0
Bellerive Plaza | Retail | Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations, Exchange
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				76,000
Gross Disposition Price				$ 0
Gain (Loss) on Sale and Transfer of Investment Properties, net	$ (22)			(22)
Gain (Loss) on Extinguishment of Debt				$ 1,694
Carrying value, surrendered properties	$ 4,771
Parkway Centre North | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				143,000
Gross Disposition Price				$ 23,700
Gain (Loss) on Sale and Transfer of Investment Properties, net				5,357
Gain (Loss) on Extinguishment of Debt				$ (1,695)
Tulsa Hills | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				473,000
Gross Disposition Price				$ 70,000
Gain (Loss) on Sale and Transfer of Investment Properties, net				13,476
Gain (Loss) on Extinguishment of Debt				$ 0
McKinney Town Center | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				243,000
Gross Disposition Price				$ 51,000
Gain (Loss) on Sale and Transfer of Investment Properties, net				15,430
Gain (Loss) on Extinguishment of Debt				$ 0
Riverstone Shopping Center | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				273,000
Gross Disposition Price				$ 27,750
Gain (Loss) on Sale and Transfer of Investment Properties, net				(320)
Gain (Loss) on Extinguishment of Debt				$ (1,540)
Hiram Pavilion | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				363,000
Gross Disposition Price				$ 44,350
Gain (Loss) on Sale and Transfer of Investment Properties, net				22,124
Gain (Loss) on Extinguishment of Debt				$ 0
Poplin Place | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				228,000
Gross Disposition Price				$ 28,300
Gain (Loss) on Sale and Transfer of Investment Properties, net				2,841
Gain (Loss) on Extinguishment of Debt				$ 0
Walden Park | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				34,000
Gross Disposition Price				$ 5,325
Gain (Loss) on Sale and Transfer of Investment Properties, net				5
Gain (Loss) on Extinguishment of Debt				$ 0
Streets of Cranberry | Retail | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Square Feet | ft²				108,000
Gross Disposition Price				$ 26,500
Gain (Loss) on Sale and Transfer of Investment Properties, net				3,276
Gain (Loss) on Extinguishment of Debt				$ 0