Real Estate Investments Business Acquisitions (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Business Acquisition [Line Items]
Purchase Price	$ 287,527	$ 248,463
Debt Assumed, Net of Premiums	0	19,933
Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets	21,649	18,741
Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets	$ 7,153	$ 14,724
Pablo Plaza [Member]
Business Acquisition [Line Items]
Date Purchased	Jan. 08, 2019
Property Name	Pablo Plaza (1)
City/State	Jacksonville, FL
Ownership	100.00%
Purchase Price	$ 600
Debt Assumed, Net of Premiums	0
Pablo Plaza [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets	0
Pablo Plaza [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets	$ 0
Melrose Market [Member]
Business Acquisition [Line Items]
Date Purchased	Feb. 08, 2019
Property Name	Melrose Market
City/State	Seattle, WA
Ownership	100.00%
Purchase Price	$ 15,515
Debt Assumed, Net of Premiums	0
Melrose Market [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets	941
Melrose Market [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets	$ 358
The Field at Commonwealth Ph II [Member]
Business Acquisition [Line Items]
Date Purchased	Jun. 18, 2019
Property Name	The Field at Commonwealth Ph II (2)
City/State	Chantilly, VA
Ownership	100.00%
Purchase Price	$ 4,083
Debt Assumed, Net of Premiums	0
The Field at Commonwealth Ph II [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets	0
The Field at Commonwealth Ph II [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets	$ 0
Culver Public Market [Member]
Business Acquisition [Line Items]
Date Purchased	Jun. 21, 2019
Property Name	Culver Public Market
City/State	Culver City, CA
Ownership	100.00%
Purchase Price	$ 1,279
Debt Assumed, Net of Premiums	0
Culver Public Market [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets	0
Culver Public Market [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets	$ 0
6401 Roosevelt [Member]
Business Acquisition [Line Items]
Date Purchased	Jun. 28, 2019
Property Name	6401 Roosevelt
City/State	Seattle, WA
Ownership	100.00%
Purchase Price	$ 3,550
Debt Assumed, Net of Premiums	0
6401 Roosevelt [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets	0
6401 Roosevelt [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets	$ 0
The Pruneyard Shopping Center [Member]
Business Acquisition [Line Items]
Date Purchased	Jul. 01, 2019
Property Name	The Pruneyard Shopping Center
City/State	Campbell, CA
Ownership	100.00%
Purchase Price	$ 212,500
Debt Assumed, Net of Premiums	0
The Pruneyard Shopping Center [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets	16,991
The Pruneyard Shopping Center [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets	$ 5,833
Circle Marina Center [Member]
Business Acquisition [Line Items]
Date Purchased	Sep. 17, 2019
Property Name	Circle Marina Center
City/State	Long Beach, CA
Ownership	100.00%
Purchase Price	$ 50,000
Debt Assumed, Net of Premiums	0
Circle Marina Center [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets	3,717
Circle Marina Center [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets	$ 962
Ballard Blocks I [Member]
Business Acquisition [Line Items]
Date Purchased		Jan. 02, 2018
Property Name		Ballard Blocks I
City/State		Seattle, WA
Ownership		49.90%
Purchase Price		$ 54,500
Debt Assumed, Net of Premiums		0
Ballard Blocks I [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets		3,668
Ballard Blocks I [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets		$ 2,350
Ballard Blocks II [Member]
Business Acquisition [Line Items]
Date Purchased		Jan. 02, 2018
Property Name		Ballard Blocks II
City/State		Seattle, WA
Ownership		49.90%
Purchase Price		$ 4,000
Debt Assumed, Net of Premiums		0
Ballard Blocks II [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets		0
Ballard Blocks II [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets		$ 0
Metuchen [Member]
Business Acquisition [Line Items]
Date Purchased		Jan. 05, 2018
Property Name		Metuchen
City/State		Metuchen, NJ
Ownership		20.00%
Purchase Price		$ 33,830
Debt Assumed, Net of Premiums		0
Metuchen [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets		3,147
Metuchen [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets		$ 1,905
Hewlett Crossing I & II [Member]
Business Acquisition [Line Items]
Date Purchased		Jan. 10, 2018
Property Name		Hewlett Crossing I & II
City/State		Hewlett, NY
Ownership		100.00%
Purchase Price		$ 30,900
Debt Assumed, Net of Premiums		9,700
Hewlett Crossing I & II [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets		3,114
Hewlett Crossing I & II [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets		$ 1,868
Rivertowns Square [Member]
Business Acquisition [Line Items]
Date Purchased		Apr. 03, 2018
Property Name		Rivertowns Square
City/State		Dobby Ferry, NY
Ownership		100.00%
Purchase Price		$ 68,933
Debt Assumed, Net of Premiums		0
Rivertowns Square [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets		4,993
Rivertowns Square [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets		$ 5,554
Crossroads Commons II [Member]
Business Acquisition [Line Items]
Date Purchased		May 18, 2018
Property Name		Crossroads Commons II
City/State		Boulder, CO
Ownership		20.00%
Purchase Price		$ 10,500
Debt Assumed, Net of Premiums		0
Crossroads Commons II [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets		447
Crossroads Commons II [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets		$ 769
Ridgewood Shopping Center [Member]
Business Acquisition [Line Items]
Date Purchased		Sep. 07, 2018
Property Name		Ridgewood Shopping Center
City/State		Raleigh, NC
Ownership		20.00%
Purchase Price		$ 45,800
Debt Assumed, Net of Premiums		10,233
Ridgewood Shopping Center [Member] | Off-Market Favorable Lease [Member]
Business Acquisition [Line Items]
Intangible Assets		3,372
Ridgewood Shopping Center [Member] | Off-Market Lease, Unfavorable [Member]
Business Acquisition [Line Items]
Intangible Assets		$ 2,278