For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Concentration of Credit Risk (Details) - property	12 Months Ended
Concentration of Credit Risk (Details) - property	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Concentration Risk [Line Items]
Number of properties	54
Pennsylvania [Member]
Concentration Risk [Line Items]
Number of properties	23
Revenues [Member] \| Ahold N.V. [Member]
Concentration Risk [Line Items]
Percentage of concentration risk	13.00%	12.00%	11.00%