Supplemental Disclosures About Natural Gas Producing Activities - Additional Information (Details) - Bcf	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Extractive Industries [Abstract]
Acquired reserves (in Bcfe)		327
Extensions, discoveries and other additions (in Bcfe)	22
Additional proved undeveloped locations, detailed analysis (in Bcfe)	19
Additional proved undeveloped locations, drilling activities (in Bcfe)	3
Negative revisions (in Bcfe)	85
Negative revisions, previous estimates (in Bcfe)	59
Negative revisions, revision of previous estimates (in Bcfe)	14
Negative revisions, due to loss of leases (in Bcfe)	12
Positive revisions, increase in commodity prices (in Bcfe)	1
Acquisition of proved reserves through minor interest acquired (in Bcfe)	1