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Fixed Assets - Depreciation Expense Relating to Fixed Assets (Detail) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Property Plant And Equipment [Abstract]        
Depreciation expense relating to fixed assets $ 417 $ 514 $ 866 $ 1,026