Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	$ 418,051	$ 548,710	$ 1,521,943	$ 1,473,475
Gain (loss) on derivative instruments	11,060	(3,537)	82,966	(1,628)
Total operating revenues	429,111	545,173	1,604,909	1,471,847
Natural gas
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	418,133	440,835	1,521,789	1,217,603
Crude oil and condensate
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	0	0	0	48,722
Brokered natural gas
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers	$ 0	$ 105,849	$ 0	203,375
Other
Disaggregation of Revenue [Line Items]
Total revenues from contracts with customers				$ 3,775