Summary Of Significant Accounting Policies (Summary Of The Activity For Company's Decommissioning Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Summary Of Significant Accounting Policies [Abstract]
Decommissioning liabilities, December 31, 2011 and 2010, respectively	$ 123,176	$ 117,716
Liabilities acquired and incurred	4,620
Liabilities settled	(4,660)	(504)
Accretion	4,670	6,752
Revision in estimated liabilities	(34,753)	(788)
Total decommissioning liabilities, Sepember 30, 2012 and 2011, respectively	93,053	123,176
Less: current portion of decommissioning liabilities at September 30, 2012 and 2011, respectively		14,956
Long-term decommissioning liabilities, September 30, 2012 and 2011, respectively	$ 93,053	$ 108,220