This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 59

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 805

-SubTopic 10

-Section 25

-Paragraph 23

-URI http://asc.fasb.org/extlink&oid=6909708&loc=d3e1043-128460

Name:	us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Property Transactions (Details Textual) (USD $)	11 Months Ended	12 Months Ended
Property Transactions (Details Textual) (USD $)	Nov. 30, 2011 sqft	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Property transactions (Textual) [Abstract]
Square footage of real estate property	775,000
Purchase Price of building	$ 134,700,000
Acquisition costs related to purchase	292,000
Gain on sale of investment properties		3,494,000	1,938,000	168,637,000
Percentage threshold for gain recognition				10.00%
CP Venture Six LLC [Member]
Property transactions (Textual) [Abstract]
Gain on sale of investment properties				$ 167,200,000