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Fair Value Disclosures - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Mar. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Equity method investment       $ 18
Equity method investment at fair value   $ 8    
Other Operating Income (Expense)        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Unrealized fair value (gains) losses on equity securities $ 1 $ 1 $ 7