Derivative Activities - Derivative Volumes Hedged and Average Hedge Prices (Parenthetical) (Detail) - 2021 Commodity Contract - Call Swaptions	Jun. 30, 2020 MMBTU / d bbl / d $ / MMBTU $ / bbl
Natural Gas
Derivative [Line Items]
Volume Hedged \| MMBTU / d	180,000
Weighted average price of hedge \| $ / MMBTU	2.82
Crude Oil
Derivative [Line Items]
Volume Hedged \| bbl / d	1,000
Weighted average price of hedge \| $ / bbl	55.00

Nominal number of units used to calculate payment on derivative.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

Name:	us-gaap_DerivativeNonmonetaryNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant