Financial Risk Management Activities - Credit Risk - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Letters of credit – Issued	$ 272	$ 284
Integrated Companies
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Accounts receivable - Trade	41.00%
Independent E&P Companies
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Accounts receivable - Trade	26.00%
National Oil Companies
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Accounts receivable - Trade	8.00%
Storage and Transportation Companies
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Accounts receivable - Trade	5.00%
Refining and Marketing Companies
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Accounts receivable - Trade	14.00%
Others
Fair Value Concentration Of Risk Financial Statement Captions [Line Items]
Accounts receivable - Trade	6.00%