Revenue From Contracts With Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
(Loss) Gain on Commodity Derivative Instruments	$ (168,834)	$ 213,913	$ (116,995)	$ 240,118
Other Revenue and Operating Income	21,155	21,841	60,463	65,299
Total Revenue and Other Operating Income	66,075	529,997	631,275	1,413,460
Natural Gas Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	163,054	245,815	561,162	966,574
NGL Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	15,053	18,305	40,691	72,095
Oil/Condensate Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	4,106	931	7,630	5,193
Total Natural Gas, NGL and Oil Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	182,213	265,051	609,483	1,043,862
Purchased Gas Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contracts with Customers	$ 31,541	$ 29,192	$ 78,324	$ 64,181