Commitments and Contingencies (Details 1) (USD $) In Millions	6 Months Ended
Jun. 30, 2011
Commitments and Contingencies (Textuals) [Abstract]
Period after which Ground lease rentals are adjusted based on fair market value and the Consumer Price Index	5 years
Annual ground lease rental obligations	$ 1.0
Contractual obligations for ground lease including annual rental obligation	The minimum rent is subject to increases every five years based on 50% of the average annual percentage rent for the previous five years
Non-refundable escrow deposits related to potential future acquisitions	$ 16.0

Carrying value of amounts transferred to third parties for security purposes that are expected to be returned or applied towards payment in the future.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 17
-Article 5

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 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_DepositsAssets
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant