Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Intangible Drilling Cost	$ 4,566,206	$ 4,120,283
Gas Gathering Equipment	2,399,883	2,126,895
Proved Gas Properties	1,157,361	1,135,411
Gas Wells and Related Equipment	1,047,139	859,359
Unproved Gas Properties	949,529	927,667
Surface Land and Other Equipment	233,812	238,487
Other	158,368	159,326
Total Property, Plant and Equipment	10,512,298	9,567,428
Less: Accumulated Depreciation, Depletion and Amortization	2,981,723	2,624,984
Total Property, Plant and Equipment—Net	$ 7,530,575	$ 6,942,444