Supplemental Information Relating To Oil And Natural Gas Producing Activities (unaudited) (Narrative) (Details)	12 Months Ended
	Dec. 31, 2015 $ / bbl $ / MMBTU	Dec. 31, 2014 $ / bbl $ / MMBTU	Dec. 31, 2013 $ / bbl $ / MMBTU
Extractive Industries [Abstract]
Valuation of proved reserves on discounted rate	10.00%
Reference prices per bbl of oil | $ / bbl	50.28	94.99	96.78
Reference prices per mmbtu of natural gas | $ / MMBTU	2.59	4.35	3.67