REAL ESTATE PROPERTIES REAL ESTATE PROPERTIES 1 (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Real Estate [Abstract]
Land	$ 308,931	$ 301,435
Investment Building and Building Improvements	1,435,309	1,393,688
Tenant Improvements	368,833	353,884
Development	293,908	170,441
Real Estate Investment Property, at Cost	2,406,981	2,219,448
Real Estate Investment Property, Accumulated Depreciation	(694,250)	(657,454)
Real Estate Investment Property, Net	$ 1,712,731	$ 1,561,994

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

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Phase
-URI http://asc.fasb.org/extlink&oid=49177889

+ Details

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Period Type:	instant

- Definition

Aggregate of the carrying amounts as of the balance sheet date of investments in building and building improvements.

+ References

+ Details

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

- Definition

Amount before accumulated depletion of real estate held for productive use, excluding land held for sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 4
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6812-107765

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.13)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- References

No definition available.

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- Definition

The cumulative amount of depreciation for real estate property held for investment purposes.

+ References

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Data Type:	xbrli:monetaryItemType
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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

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Amount of real estate investment property, net of accumulated depreciation, 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

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- Definition

Carrying amount as of the balance sheet date of improvements having a life longer than one year that were made for the benefit of one or more tenants.

+ References

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