Employee Benefits - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Amount paid in severance benefits over the period	$ 123
Post employment benefits liability	471
Pension
Defined Benefit Plan Disclosure [Line Items]
Severance Charges	(182)	$ 96
(Credit) charge due to change in discount rate assumption	(196)	54
(Charge) credit due to difference between estimated and actual return on assets		(150)
Pension | Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Employer discretionary contribution amount	$ 0	$ 300