Dispositions and Assets Held for Sale (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) property shopping_center	Mar. 31, 2019 USD ($) shopping_center	Dec. 31, 2019 property
Schedule of Acquisitions and Dispositions [Line Items]
Gain on sale	$ 8,905	$ 7,602
Disposed of by Sale
Schedule of Acquisitions and Dispositions [Line Items]
Number of shopping centers sold | shopping_center	3	3
Number of partial shopping centers sold | shopping_center	2
Proceeds from sale of property	$ 40,500	$ 44,900
Gain on sale	7,500	7,300
Provisions of impairment	100
Disposed of by Sale | Previously Disposed Assets
Schedule of Acquisitions and Dispositions [Line Items]
Proceeds from sale of property	900	300
Gain on sale	1,400	$ 300
Contingencies received	$ 500
Held-for-sale
Schedule of Acquisitions and Dispositions [Line Items]
Number of real estate properties | property	2		2
Held-for-sale | Partial Properties
Schedule of Acquisitions and Dispositions [Line Items]
Number of real estate properties | property			2