Supplemental Disclosure to Statements of Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Supplemental Disclosure [Line Items]
Write-off of fully depreciated property and deferred costs	$ 31,069	$ 16,591	$ 35,658
Write Off Of Depreciated Property And Deferred Costs Due To Sale	106,698	110,414	12,715
Write-off of preferred units costs due to redemption	2,806	0	0
Assumption of mortgage loans in connection with the acquisition of properties	(12,537)	0	(2,833)
Equity contribution from unconsolidated joint venture partner	0	3,500	0
Issuance of preferred units, noncash transaction	$ 0	$ 16,597	$ 0