Real Estate - Development/Redevelopment (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Real Estate Properties [Line Items]
Properties under development or held for future development	$ 49,065	$ 40,232
Real estate investment property, at cost	2,830,144	$ 2,685,403
Army Navy Building [Domain]
Real Estate Properties [Line Items]
Properties under development or held for future development	4,400
Real estate investment property, at cost	4,300
The Wellington land parcel [Member]
Real Estate Properties [Line Items]
Properties under development or held for future development	27,300
Riverside Developments [Member]
Real Estate Properties [Line Items]
Properties under development or held for future development	19,000
Spring Vally Retail Center [Member]
Real Estate Properties [Line Items]
Properties under development or held for future development	$ 2,500

The current amount of expenditures for a real estate project that has not yet been completed.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.10)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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- Definition

Amount of real estate investment property which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(d))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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- Definition

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.

+ References

No definition available.

+ Details

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- Details

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- Details

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- Details

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- Details

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