Supplemental Oil and Gas Disclosures (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 MBoe	Dec. 31, 2013 MBoe	Dec. 31, 2012 MBoe	Dec. 31, 2011 MBoe
Proved reserves	12,245,000	23,538,000	25,671,000	22,718,000
Standard measure of discounted future net cash flows	$ 523,735	$ 535,682	$ 498,978	$ 264,872
Discount Rate Applied To Cash Flow Amounts In Computation Of Standardized Measure Of Discounted Future Net Cash Flows	10.00%
PUD Reserves Transfer [Member]
Probable reserves	8.0
Standard measure of discounted future net cash flows	$ 75,000
Columbus Field Transfer [Member]
Contingent resources	1.8