Supplemental Gas Data Capitalized Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Extractive Industries [Abstract]
Intangible Drilling Cost	$ 4,120,283	$ 3,849,689
Proved Gas Properties	1,135,411	1,999,891
Gas gathering assets	1,099,047	1,182,234
Unproved gas properties	927,667	919,733
Gas wells and related equipment	856,973	834,120
Other gas assets	54,395	181,038
Total Property, Plant and Equipment	8,193,776	8,966,705
Accumulated Depreciation, Depletion and Amortization	(2,475,917)	(3,408,606)
Net Capitalized Costs	$ 5,717,859	$ 5,558,099