The charge against earnings in the period to reduce the carrying amount of real property to fair value.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109226691&loc=d3e2921-110230

Name:	us-gaap_ImpairmentOfRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Real Estate (Narrative) (Details) - USD ($)	3 Months Ended	6 Months Ended
Real Estate (Narrative) (Details) - USD ($)	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Real Estate Properties [Line Items]
Impairment charges	$ 9,850,000	$ 21,396,000	$ 9,850,000
Carll's Corner [Member]
Real Estate Properties [Line Items]
Location		Bridgeton, New Jersey
Maxatawny Marketplace [Member]
Real Estate Properties [Line Items]
Location		Maxatawny, Pennsylvania
West Bridgewater Plaza [Member]
Real Estate Properties [Line Items]
Location		West Bridgewater, Massachusetts