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Financial Instruments and Risk Management - Fair Value Information on Other Financial Assets and Liabilities Recorded at Amortized Cost (Parenthetical) (Detail) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Conversion features of the instruments value | $ 215 |
Estimate Fair Value [Member] | Senior Unsecured Convertible Bonds Issued on July 3, 2017 Tranche A [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Senior unsecured convertible bonds |  | $ 1,030

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