Fair value as of the balance sheet date of all interest rate derivative liabilities designated as cash flow hedging instruments.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 17

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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_InterestRateCashFlowHedgeLiabilityAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Mortgage Loans Payable And Secured Revolving Credit Facilities (Derivative Financial Instruments) (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Jan. 20, 2010
Derivative [Line Items]
Mortgage loans payable subject to interest rate swaps	$ 31,417,000	$ 32,091,000
Liabilities related to the fair value of interest swaps of mortgage loans payable	1,577,000	2,053,000
Cash paid to terminate interest rate swaps			$ 5,500,000
Minimum [Member]
Derivative [Line Items]
Fixed annual interest rate	5.20%
Maximum [Member]
Derivative [Line Items]
Fixed annual interest rate	6.50%