Fixed Assets And Asset Retirement Obligations Depreciation Expense (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 9,077	$ 5,804	$ 17,827	$ 11,640