Business Segments (Details 1) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Total assets	$ 6,283,769	$ 6,190,004
Corporate Non-Segment [Member]
Segment Reporting Information [Line Items]
Total assets	440,278	414,802
Same Store [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total assets	4,148,435	4,148,787
Redevelopment and Development [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total assets	822,348	792,126
Acquisition [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total assets	546,467	507,190
Other Real Estate [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total assets	$ 326,241	$ 327,099