Exit and Termination Costs - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended					9 Months Ended
	Aug. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Restructuring Cost And Reserve [Line Items]
One-time minimum volume commitment contract payment		$ 28,500,000			$ 0		$ 28,500,000	$ 0
Restructuring Charges		521,633,000			819,000		533,525,000	3,025,000
Severance costs		4,191,000			819,000		5,638,000	3,000,000
Workforce Reduction
Restructuring Cost And Reserve [Line Items]
Severance costs		3,700,000				$ 2,200,000
North Louisiana
Restructuring Cost And Reserve [Line Items]
Exit cost	$ 479,800,000
Severance costs		2,500,000
Pennsylvania
Restructuring Cost And Reserve [Line Items]
Exit cost		$ 233,000			0		$ 10,678,000	$ 0
Pennsylvania | Capacity Releases on Transportation Pipelines
Restructuring Cost And Reserve [Line Items]
Exit cost			$ 10,400,000
Northwest Pennsylvania
Restructuring Cost And Reserve [Line Items]
Severance costs				$ 1,600,000
Northwest Pennsylvania | Non-Core Assets
Restructuring Cost And Reserve [Line Items]
Severance costs					$ 819,000