Real Estate (Schedule Of Transactions Related To Properties Held For Sale/Conveyance) (Details) - Disposal Group, Held-for-sale, Not Discontinued Operations [Member] - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Real Estate Properties [Line Items]
Sales Price	$ 19,600,000	$ 12,850,000	$ 98,250,000
Gain on Sale	$ 4,864,000	$ 7,099,000
Mechanicsburg Center [Member]
Real Estate Properties [Line Items]
Location	Mechanicsburg, PA
Date Sold	Aug. 28, 2018
Sales Price	$ 16,100,000
Gain on Sale	$ 4,864,000
West Bridgewater Plaza [Member]
Real Estate Properties [Line Items]
Location	West Bridgewater, MA
Date Sold	Sep. 28, 2018
Sales Price	$ 3,500,000
Outparcel Building Adjacent to Camp Hill [Member]
Real Estate Properties [Line Items]
Location		Camp Hill, PA
Date Sold		Feb. 01, 2017
Sales Price		$ 10,650,000
Gain on Sale		$ 7,099,000
Fredericksburg Way [Member]
Real Estate Properties [Line Items]
Location		Fredericksburg, VA
Date Sold		Dec. 29, 2017
Sales Price		$ 2,200,000
Liberty Marketplace [Member]
Real Estate Properties [Line Items]
Location			Dubois, PA
Date Sold			Feb. 11, 2016
Sales Price			$ 15,000,000
Upland Square [Member]
Real Estate Properties [Line Items]
Location			Pottstown, PA
Date Sold			Nov. 02, 2016
Sales Price			$ 83,250,000