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Supplemental Oil And Gas Information (Schedule Of Changes In The Standardized Measure Of Discounted Future Net Cash Flows From Proved Oil And Gas Reserves) (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Supplemental Oil And Gas Information [Abstract]      
Balance, beginning of year $ 51,909 $ 48,344 $ 28,187
Sales, net of production costs and taxes (14,275) (11,552) (7,568)
Discoveries and extensions, net of costs 6,967 10,923 2,099
Purchase of reserves in place         
Sale of reserves in place         
Net changes in prices and production costs (6,067) 15,428 15,554
Revisions of quantity estimates (9,883) 343 8,873
Previously estimated development cost incurred during the year 8,760 5,346 3,806
Changes in future development costs (1,919) (1,109) (3,168)
Changes in production rates (timing) and other (5,657) (2,336) (2,037)
Accretion of discount 6,223 4,376 2,598
Net change in income taxes 9,296 (17,854)  
Balance, end of year $ 45,354 $ 51,909 $ 48,344