Related Party Transactions (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) property	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Melvin Simon & Associates, Inc. \| Amounts for services provided
Related Party Transactions
Amounts charged to related party	$ 0.6	$ 0.6	$ 0.6
Properties owned by related parties \| Amounts for services provided
Related Party Transactions
Number of shopping centers owned by related parties in which management services are provided \| property	2
Amounts charged to related party	$ 3.9	4.2	4.2
Unconsolidated Joint Ventures \| Amounts for services provided
Related Party Transactions
Amounts charged to related party	108.2	111.5	116.4
Unconsolidated Joint Ventures \| Development, royalty and other fees
Related Party Transactions
Amounts charged to related party	$ 14.8	$ 16.0	$ 15.5

Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07.1(c))
-URI http://asc.fasb.org/extlink&oid=116637345&loc=SL114874292-224272

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(e))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration