The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 159

-Paragraph 18

-Subparagraph f

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 20

-Subparagraph a (1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

PRINCIPLES OF CONSOLIDATION (Details)	3 Months Ended
PRINCIPLES OF CONSOLIDATION (Details)	Mar. 31, 2013 joint_ventures	Mar. 31, 2013 University Business Center [Member]	Dec. 31, 2012 University Business Center [Member]	Mar. 31, 2013 Castilian Research Center [Member]	Dec. 31, 2012 Castilian Research Center [Member]	Mar. 31, 2013 Industry Distribution Center II [Member]	Dec. 31, 2012 Industry Distribution Center II [Member]
Subsidiaries [Line Items]
Joint Ventures	2
Joint venture ownership interest		80.00%	80.00%	80.00%	80.00%
Joint ventures' assets, liabilities, revenues and expenses with noncontrolling interests		100.00%	100.00%	100.00%	100.00%
Tenant-in-common interest						50.00%	50.00%