Commitments and Contingencies - Property Damage from Natural Disaster (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2019
Jacksonville Mall, Jacksonville, North Carolina
Loss Contingencies [Line Items]
Net recoveries	$ 1.9	$ 1.6

Amount of excess (deficiency) of insurance recovery over the loss incurred from an insured event.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 30
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6397426&loc=d3e17499-108355

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