Related Party Transactions (Schedule of Fees Earned from Related Parties) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Management Fees [Member]
Revenue from related party transactions	$ 2,725	$ 2,646	$ 5,455	$ 4,623
Leasing Fees [Member]
Revenue from related party transactions	940	997	2,234	2,801
Construction and Development Fees [Member]
Revenue from related party transactions	$ 912	$ 814	$ 1,755	$ 2,396

Revenues, net of returns and allowances, realized from sales and other transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party during the period.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 57

-Paragraph 2

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 850

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Name:	us-gaap_RelatedPartyTransactionRevenuesFromTransactionsWithRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration