Supplemental Information on Oil and Gas Producing Activities (Unaudited) (Details 2) MMcfe in Thousands	12 Months Ended
	Dec. 31, 2015 MMcfe Bcf MMBbls	Dec. 31, 2014 MMcfe Bcf MMBbls	Dec. 31, 2013 MMcfe Bcf MMBbls
Proved developed and undeveloped reserves:
Balance at the beginning of the period | MMcfe	12,683	7,632	4,929
Revisions | MMcfe	(1,801)	(1,054)	(788)
Extensions, discoveries and other additions | MMcfe	2,878	6,444	3,682
Production | MMcfe	(545)	(368)	(191)
Purchase of reserves | MMcfe		29
Proved Developed and Undeveloped Reserve, Net (Energy), Ending Balance | MMcfe	13,215	12,683	7,632
Oil and Gas Reserves
Proved developed reserves | MMcfe	5,838	3,803	2,022
Proved undeveloped reserves | MMcfe	7,377	8,880	5,610
Natural gas
Proved developed and undeveloped reserves:
Balance at the beginning of the period | Bcf	10,535	6,753	3,694
Revisions | Bcf	(2,816)	(1,025)	152
Extensions, discoveries and other additions | Bcf	2,253	5,095	3,084
Production | Bcf	(439)	(317)	(177)
Purchase of reserves | Bcf		29
Balance at the end of the period | Bcf	9,533	10,535	6,753
Oil and Gas Reserves
Proved developed reserves | Bcf	3,627	3,285	1,818
Proved undeveloped reserves | Bcf	5,906	7,250	4,936
NGLS
Proved developed and undeveloped reserves:
Balance at the beginning of the period	330	137	203
Revisions	176	(6)	(140)
Extensions, discoveries and other additions	97	206	76
Production	(16)	(7)	(2)
Balance at the end of the period	587	330	137
Oil and Gas Reserves
Proved developed reserves	360	80	33
Proved undeveloped reserves	227	250	105
Oil and condensate
Proved developed and undeveloped reserves:
Balance at the beginning of the period	28	10	3
Revisions	(8)
Extensions, discoveries and other additions	8	19	7
Production	(2)	(1)
Balance at the end of the period	26	28	10
Oil and Gas Reserves
Proved developed reserves	8	6	2
Proved undeveloped reserves	18	22	8