Exit and Termination Costs - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Restructuring Cost And Reserve [Line Items]
Restructuring Charges	$ (15,946)	$ 10,297		$ (2,232)	$ 11,892
Severance costs	0	(148)		509	1,447
North Louisiana
Restructuring Cost And Reserve [Line Items]
Accretion expense				25,000
Exit cost				436,100
Restructuring Charges	28,200
Pennsylvania
Restructuring Cost And Reserve [Line Items]
Exit cost	$ 184	$ 10,445		394	$ 10,445
Pennsylvania | Capacity Releases on Transportation Pipelines
Restructuring Cost And Reserve [Line Items]
Exit cost				$ 8,400
Northwest Pennsylvania
Restructuring Cost And Reserve [Line Items]
Severance costs			$ 1,600