Summary of Significant Accounting Policies (Revenue Recognition) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2018
Real Estate Tenant Receivables
Financing Receivable, Impaired [Line Items]
Allowance for doubtful accounts receivable	$ 1.3	$ 1.5
Deferred Operating Lease
Financing Receivable, Impaired [Line Items]
Allowance for doubtful accounts receivable	1.3	$ 1.8
Real Estate Sales \| Lennar
Financing Receivable, Impaired [Line Items]
Interest income from settlement of real estate tax reimbursements	$ 123.4

For an unclassified balance sheet, a valuation allowance for receivables due a company that are expected to be uncollectible.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5074-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.4)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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