Supplemental Information On Oil And Gas Exploration And Production Activities (Unaudited) - Net Changes in Capitalized Exploratory Well Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Extractive Industries [Abstract]
Balance, beginning of year	$ 0	$ 0	$ 2,032
Additions to capitalized exploratory well costs pending the determination of proved reserves			64
Capitalized exploratory well costs charged to expense			(2,096)
Balance, end of year	$ 0	$ 0	$ 0