Revenue - Additional Information (Detail) $ in Millions	9 Months Ended
Sep. 30, 2019 USD ($)
Exploration and Production
Disaggregation Of Revenue [Line Items]
Credit losses on receivables with customers	$ 0

Amount of expense (reversal of expense) for expected credit loss on right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919249-210447

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Name:	us-gaap_ContractWithCustomerAssetCreditLossExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration