Supplemental Information On Oil And Gas Exploration And Production Activities (Unaudited) - Schedule Of Standardized Measure (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Extractive Industries [Abstract]
Future cash inflows	$ 346,948	$ 481,131	$ 1,464,138
Future production costs	(172,062)	(192,349)	(427,113)
Future development costs	(29,814)	(91,725)	(312,010)
Future income tax expense			(180,248)
Future net cash flows	145,072	197,057	544,767
10% annual discount for estimated timing of cash flows	(59,189)	(92,661)	(288,911)
Standardized measure of discounted future cash flows	$ 85,883	$ 104,396	$ 255,856	$ 125,357