Employee Benefits - Other Pre-tax Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive (Income) Loss (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (benefit)	$ 0	$ 0	$ 0
Reversal of amortization items
Prior service cost (benefit)	(61)	(61)	(61)
Total recognized in Other comprehensive loss (income) (pre-tax)	(61)	(61)	(61)
Health Care and Life
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (benefit)	0	0	(22)
Reversal of amortization items
Prior service cost (benefit)	894	966	971
Total recognized in Other comprehensive loss (income) (pre-tax)	$ 894	$ 966	$ 949