Supplemental Disclosure to Statements of Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Supplemental Disclosure to Statements of Cash Flows [Abstract]
Write off of fully depreciated/amortized property and deferred costs	$ 7,182	$ 7,643
Write Off Of Depreciated/Amortized Property And Deferred Costs Due To Sale	23,906	3,331
Discount on preferred unit redemption net of origination costs	$ 0	$ 2,771