Accounting Policies (Accounting for Historic and New Markets Tax Credits) (Details)	Dec. 31, 2016 property
Business Acquisition [Line Items]
Number of real estate properties	1,300
Life Sciences Acquisitions
Business Acquisition [Line Items]
Number of real estate properties	11
Development Assets \| Life Sciences Acquisitions
Business Acquisition [Line Items]
Number of real estate properties	2

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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