Rental Property Revenues (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Operating Leases Future Minimum Payments Receivable [Abstract]
2011	$ 105,491
2012	106,025
2013	103,087
2014	95,820
2015	84,934
Thereafter	319,922
Total Rentals	815,279
Office [Member]
Operating Leases Future Minimum Payments Receivable [Abstract]
2011	82,153
2012	81,797
2013	79,737
2014	73,031
2015	65,992
Thereafter	268,816
Total Rentals	651,526
Retail [Member]
Operating Leases Future Minimum Payments Receivable [Abstract]
2011	23,338
2012	24,228
2013	23,350
2014	22,789
2015	18,942
Thereafter	51,106
Total Rentals	$ 163,753

Future minimum rental payments in aggregate as of the balance sheet date under operating leases.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 23

-Subparagraph b(ii)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 840

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6454179&loc=d3e41551-112718

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- Definition

Future rental payments receivable within one year of the balance sheet date under an operating lease.

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- Definition

Future rental payments receivable within the fifth year from the balance sheet date under an operating lease.

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Future rental payments receivable within the fourth year from the balance sheet date under an operating lease.

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Future rental payments receivable within the third year from the balance sheet date under an operating lease.

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Future rental payments receivable within the second year from the balance sheet date under an operating lease.

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- Definition

Future minimum lease payments receivable under operating leases for periods greater than five years following the balance sheet date.

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