Oil and Gas Properties (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Proven Properties [Abstract]
Acquisition, equipment, exploration, drilling and evnironmental costs	$ 10,480,165	$ 9,731,407
Less: Accumulated depletion, depreciation and amortization	(9,629,020)	(6,094,764)
Proved	851,145	3,636,643
Unproven Properties:
Unproven properties not being amortized	0	242,294
Net capitalized costs - oil and gas properties	$ 851,145	$ 3,878,937