Employee Benefits - Additional Information (Detail) - USD ($)	3 Months Ended					9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Amount paid in severance benefits over the period						$ 209,000,000
Post employment benefits liability	$ 430,000,000					430,000,000
Pension
Defined Benefit Plan Disclosure [Line Items]
Remeasurement gain (loss), net	(1,092,000,000)	$ (153,000,000)	$ (182,000,000)	$ (291,000,000)	$ 96,000,000	(1,427,000,000)	$ (195,000,000)
(Credit) charge due to change in discount rate assumption	1,800,000,000		$ 196,000,000	589,000,000
(Charge) credit due to difference between estimated and actual return on assets	$ 689,000,000	$ (163,000,000)		$ 298,000,000
Pension | Qualified Plan
Defined Benefit Plan Disclosure [Line Items]
Employer discretionary contribution amount						$ 0	$ 300,000,000