Supplemental Disclosure to Statements of Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Supplemental Cash Flow Information [Abstract]
Write-off of fully depreciated property and deferred costs	$ 27,020	$ 12,364
Write-off Of Depreciated Property And Deferred Costs Due To Sale	95,093	107,456
Write-off of origination costs relating to preferred unit redemptions	$ 2,806	$ 0