Summary of Significant Accounting Policies - Asset Retirement Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Asset retirement obligations
Asset retirement obligation as of beginning of period	$ 287,805	$ 443,349
Accretion expense	13,733	17,513
Liabilities incurred	8,985	7,785
Liabilities settled	(3,569)	(3,722)
Liabilities assumed in the Rice Merger	0	27,999
Liabilities removed due to divestitures	(5,535)	(231,936)
Change in estimates	160,402	26,817
Asset retirement obligation as of end of period	$ 461,821	$ 287,805