Investments in Real Estate Partnerships - Schedule of Acquisitions by Real Estate Partnerships (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Ownership Percentage		0.00%	0.00%
Purchase Price		$ 287,527	$ 116,239
Debt Assumed, Net of Premiums		0	9,700
Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets		7,153	7,422
Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets		$ 21,649	8,371
Unconsolidated Properties [Member]
Business Acquisition [Line Items]
Purchase Price			346,862
Debt Assumed, Net of Premiums			100,233
Unconsolidated Properties [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets			12,952
Unconsolidated Properties [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets			$ 13,889
Unconsolidated Properties [Member] | Ballard Blocks I [Member]
Business Acquisition [Line Items]
Date Purchased			Jan. 02, 2018
Property Name			Ballard Blocks I
City/State			Seattle, WA
Business Acquisition, Description of Acquired Entity			Operating
Business Acquisition, Co-investment Partner			Other
Ownership Percentage			49.90%
Purchase Price			$ 54,500
Unconsolidated Properties [Member] | Ballard Blocks I [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets			2,350
Unconsolidated Properties [Member] | Ballard Blocks I [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets			$ 3,668
Unconsolidated Properties [Member] | Ballard Blocks II [Member]
Business Acquisition [Line Items]
Date Purchased			Jan. 02, 2018
Property Name			Ballard Blocks II
City/State			Seattle, WA
Business Acquisition, Description of Acquired Entity			Development
Business Acquisition, Co-investment Partner			Other
Ownership Percentage			49.90%
Purchase Price			$ 4,000
Unconsolidated Properties [Member] | Metuchen [Member]
Business Acquisition [Line Items]
Date Purchased			Jan. 05, 2018
Property Name			The District at Metuchen
City/State			Metuchen, NJ
Business Acquisition, Description of Acquired Entity			Operating
Business Acquisition, Co-investment Partner			Columbia II
Ownership Percentage			20.00%
Purchase Price			$ 33,830
Unconsolidated Properties [Member] | Metuchen [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets			1,905
Unconsolidated Properties [Member] | Metuchen [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets			$ 3,147
Unconsolidated Properties [Member] | Crossroad Commons II [Member]
Business Acquisition [Line Items]
Date Purchased			May 18, 2018
Property Name			Crossroads Commons II
City/State			Boulder, CO
Business Acquisition, Description of Acquired Entity			Operating
Business Acquisition, Co-investment Partner			Columbia I
Ownership Percentage			20.00%
Purchase Price			$ 10,500
Unconsolidated Properties [Member] | Crossroad Commons II [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets			769
Unconsolidated Properties [Member] | Crossroad Commons II [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets			$ 447
Unconsolidated Properties [Member] | Ridgewood [Member]
Business Acquisition [Line Items]
Date Purchased			Sep. 07, 2018
Property Name			Ridgewood Shopping Center
City/State			Raleigh, NC
Business Acquisition, Description of Acquired Entity			Operating
Business Acquisition, Co-investment Partner			Columbia II
Ownership Percentage			20.00%
Purchase Price			$ 45,800
Debt Assumed, Net of Premiums			10,233
Unconsolidated Properties [Member] | Ridgewood [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets			2,278
Unconsolidated Properties [Member] | Ridgewood [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets			$ 3,372
Unconsolidated Properties [Member] | Shoppes at Bartram Park [Member]
Business Acquisition [Line Items]
Date Purchased			Dec. 17, 2018
Property Name			Shoppes at Bartram Park
City/State			Jacksonville, FL
Business Acquisition, Description of Acquired Entity	[1]		Operating (1)
Business Acquisition, Co-investment Partner			Other
Ownership Percentage			50.00%
Purchase Price			$ 984
Unconsolidated Properties [Member] | Town and Country [Member]
Business Acquisition [Line Items]
Date Purchased			Dec. 14, 2018
Property Name			Town and Country Center
City/State			Los Angeles, CA
Business Acquisition, Description of Acquired Entity			Operating
Business Acquisition, Co-investment Partner			Other
Ownership Percentage			9.38%
Purchase Price			$ 197,248
Debt Assumed, Net of Premiums			90,000
Unconsolidated Properties [Member] | Town and Country [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets			5,650
Unconsolidated Properties [Member] | Town and Country [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets			$ 3,255

[1] Land parcels purchased as additions to the existing operating property.