Supplemental Disclosure to Statements of Cash Flows (Details) (USD $) In Thousands	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Supplemental Disclosure [Line Items]
Write-off of fully depreciated property and deferred costs	$ 12,364	$ 31,610
Write Off Of Depreciated Property And Deferred Costs Due To Sale	$ 107,456	$ 0