Financial Risk Management Activities - Notional Amounts of Outstanding Financial Risk Management Derivative Contracts (Detail) MMBbls in Millions	Mar. 31, 2020 USD ($) MMBbls	Dec. 31, 2019 USD ($) MMBbls
Commodity
Derivative [Line Items]
Commodity - crude oil (millions of barrels) \| MMBbls	41.3	54.9
Foreign Exchange
Derivative [Line Items]
Outstanding gross notional amount	$ 65,000,000	$ 90,000,000
Interest Rate Swaps \| Designated as Fair Value Hedges
Derivative [Line Items]
Outstanding gross notional amount	$ 100,000,000	$ 100,000,000

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No definition available.

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Nominal number of units used to calculate payment on derivative.

+ References

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

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Nominal or face amount used to calculate payment on derivative.

+ References

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