Commitments and Contingencies - Property Damage from Natural and Other Disaster (Details) - Cherry Hill Mall in Cherry Hill, New Jersey - USD ($) $ in Millions	1 Months Ended	3 Months Ended
Apr. 30, 2020	Mar. 31, 2021
Loss Contingencies [Line Items]
Net cost		$ 0.6
Business interruption recoveries	$ 0.6

The net amount (to the extent disclosed within this portion of the income statement) by which an insurance settlement exceeds incremental costs incurred from the event causing an interruption of business, plus the insurance award for earnings lost from the event, such as a natural catastrophe, explosion or fire.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=114868897&loc=SL114872001-224240

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration