Supplemental Information On Oil And Gas Exploration And Production Activities (Unaudited) (Costs Incurred In Oil and Gas Property Acquisition and Development Activities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Acquisition	$ 810,755	$ 440,288	$ 338,153
Development of proved undeveloped properties	642,811	864,511	408,121
Exploratory	0	2,249	26,174
Recompletions	13,894	45,658	44,633
Capitalized asset retirement obligation	8,800	2,095	3,556
Total	1,476,260	1,354,801	820,637
Diamondback Energy, Inc
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Acquisition	0	0	44,534
Development of proved undeveloped properties	0	0	6,369
Exploratory	0	0	17,491
Capitalized asset retirement obligation	0	0	50
Total	0	0	68,444
Investment in Grizzly Oil Sands ULC
Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items]
Acquisition	396	1,230	0
Development of proved undeveloped properties	$ 47	7,107	0
Exploratory		0	0
Capitalized asset retirement obligation	$ 282	1,055	0
Total	$ 725	$ 9,392	$ 0