Supplemental Gas Data Average Unit Prices (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) MMcf	Dec. 31, 2015 USD ($) MMcf	Dec. 31, 2014 USD ($) MMcf	Dec. 31, 2013 MMcf
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Proved Developed and Undeveloped Reserves, Sales of Minerals in Place	(870,884,000)
Oil and Gas Delivery Commitments and Contracts, Remaining Contractual Volume	431.4
Proved Developed and Undeveloped Reserves, Production	394,387,000	328,657,000	235,714,000
Proved Developed and Undeveloped Reserves, Purchases of Minerals in Place	1,443,642,000
Beginning reserves	6,251,648,000	5,642,989,000	6,827,616,000	5,731,214,000
Proved Developed and Undeveloped Reserves, Revisions of Previous Estimates	(99,849,000)	1,368,909,000	218,168,000
Proved Developed and Undeveloped Reserves, Improved Recovery	190,009,000	(3,159,421,000)	15,512,000
Proved Developed and Undeveloped Reserves, Extensions, Discoveries, and Additions	720,146,000	934,542,000	1,098,436,000
Plan and Other Revisions [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Proved Developed and Undeveloped Reserves, Extensions, Discoveries, and Additions	4,906,000
Natural Gas [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Proved Developed and Undeveloped Reserves, Sales of Minerals in Place	(711,155,000)
Proved Developed and Undeveloped Reserves, Production	358,474,000	285,041,000	216,260,000
Proved Developed and Undeveloped Reserves, Purchases of Minerals in Place	1,352,759,000
Beginning reserves	5,828,398,000	5,060,214,000	6,317,600,000	5,585,107,000
Proved Developed and Undeveloped Reserves, Revisions of Previous Estimates	21,280,000	1,052,978,000	(46,560,000)
Proved Developed and Undeveloped Reserves, Improved Recovery	179,914,000	(2,866,123,000)	15,512,000
Proved Developed and Undeveloped Reserves, Extensions, Discoveries, and Additions	643,688,000	840,800,000
Natural Gas [Member] | Plan and Other Revisions [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Proved Developed and Undeveloped Reserves, Extensions, Discoveries, and Additions			979,801,000
Natural Gas, Per Thousand Cubic Feet [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Average Gas Sales Price before effects of financial settlements | $	$ 2.01	$ 2.22	$ 4.27
Average effects of financial settlements (per thousand cubic feet) | $	0.62	0.60	0.10
Average gas sales price including effects of financial settlements (per thousand cubic feet) | $	$ 2.63	$ 2.82	$ 4.37
Average lifting costs, excluding ad valorem and severance taxes (per thousand cubic feet)	.24	.37	.59
Natural Gas Liquids [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Proved Developed and Undeveloped Reserves, Sales of Minerals in Place	(22,382,000)
Proved Developed and Undeveloped Reserves, Production	5,119,000	5,812,000	2,578,000
Proved Developed and Undeveloped Reserves, Purchases of Minerals in Place	13,177,000
Beginning reserves	60,532,000	86,212,000	77,790,000	21,546,000
Proved Developed and Undeveloped Reserves, Revisions of Previous Estimates	(20,669,000)	45,993,000	40,363,000
Proved Developed and Undeveloped Reserves, Improved Recovery	1,647,000	(45,675,000)	0
Proved Developed and Undeveloped Reserves, Extensions, Discoveries, and Additions	10,960,000	13,916,000
Natural Gas Liquids [Member] | Plan and Other Revisions [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Proved Developed and Undeveloped Reserves, Extensions, Discoveries, and Additions			18,459,000
Crude Oil [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Proved Developed and Undeveloped Reserves, Sales of Minerals in Place	(4,240,000)
Proved Developed and Undeveloped Reserves, Production	867,000	1,458,000	664,000
Proved Developed and Undeveloped Reserves, Purchases of Minerals in Place	1,970,000
Beginning reserves	10,007,000	10,915,000	7,212,000	2,806,000
Proved Developed and Undeveloped Reserves, Revisions of Previous Estimates	481,000	6,662,000	3,756,000
Proved Developed and Undeveloped Reserves, Improved Recovery	35,000	(3,208,000)	0
Proved Developed and Undeveloped Reserves, Extensions, Discoveries, and Additions	1,783,000	1,707,000
Crude Oil [Member] | Plan and Other Revisions [Member]
Average Sales Price and Production Costs Per Unit of Production [Line Items]
Proved Developed and Undeveloped Reserves, Extensions, Discoveries, and Additions			1,314,000