Natural Gas Producing Activities (Unaudited) - Schedule of the Entity's Proved and Unproved Reserves (Details)	12 Months Ended
	Dec. 31, 2017 MBbls MMcf	Dec. 31, 2016 MBbls MMcf	Dec. 31, 2015 MBbls MMcf
Proved developed and undeveloped reserves:
Beginning of year	13,508,407	9,976,597	10,738,948
Revision of previous estimates	(2,766,981)	(472,285)	(2,194,675)
Purchase	9,389,638	2,395,776	0
Sale	(2,646)	0	(61)
Extensions, discoveries and other additions	2,225,141	2,384,682	2,051,071
Production	(907,892)	(776,363)	(618,686)
End of year	21,445,667	13,508,407	9,976,597
Proved developed reserves:
Beginning of year	6,842,958	6,279,557	4,826,387
End of year	11,297,956	6,842,958	6,279,557
Proved undeveloped reserves:
Beginning of year	6,665,449	3,697,040	5,912,561
End of year	10,147,711	6,665,449	3,697,040
Natural Gas
Proved developed and undeveloped reserves:
Beginning of year	12,331,867	9,110,311	9,775,954
Revision of previous estimates	(2,760,467)	(607,171)	(2,059,531)
Purchase	8,890,145	2,288,166	0
Sale	(1,210)	0	(61)
Extensions, discoveries and other additions	2,164,578	2,241,528	1,955,935
Production	(794,677)	(700,967)	(561,986)
End of year	19,830,236	12,331,867	9,110,311
Proved developed reserves:
Beginning of year	6,074,958	5,652,989	4,257,377
End of year	10,152,543	6,074,958	5,652,989
Proved undeveloped reserves:
Beginning of year	6,256,909	3,457,322	5,518,577
End of year	9,677,693	6,256,909	3,457,322
Oil
Proved developed and undeveloped reserves:
Beginning of year | MBbls	6,395	5,900	5,005
Revision of previous estimates | MBbls	5,103	1,159	1,219
Purchase | MBbls	355	3	0
Sale | MBbls	(139)	0	0
Extensions, discoveries and other additions | MBbls	9	62	419
Production | MBbls	(992)	(729)	(743)
End of year | MBbls	10,731	6,395	5,900
Proved developed reserves:
Beginning of year | MBbls	6,395	5,900	5,005
End of year | MBbls	10,731	6,395	5,900
Proved undeveloped reserves:
Beginning of year | MBbls	0	0	0
End of year | MBbls	0	0	0
Cubic feet per thousand barrel (in mmcf)	6
Natural Gas Liquids
Proved developed and undeveloped reserves:
Beginning of year | MBbls	189,695	138,481	155,494
Revision of previous estimates | MBbls	(6,189)	21,322	(23,743)
Purchase | MBbls	82,894	17,932	0
Sale | MBbls	(100)	0	0
Extensions, discoveries and other additions | MBbls	10,084	23,797	15,437
Production | MBbls	(17,877)	(11,837)	(8,707)
End of year | MBbls	258,507	189,695	138,481
Proved developed reserves:
Beginning of year | MBbls	121,605	98,528	89,830
End of year | MBbls	180,170	121,605	98,528
Proved undeveloped reserves:
Beginning of year | MBbls	68,090	39,953	65,664
End of year | MBbls	78,337	68,090	39,953
Cubic feet per thousand barrel (in mmcf)	6