Employee Benefit Plans (Change in Accumulated Other Comprehensive Loss (Pretax) Relating to Defined Benefit Pension and Other Postretirement Benefits) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss arising during the year	$ 82
New prior service credit	4
Amortization of actuarial loss	15	$ 8	$ 19
Amortization of prior service credit	59	57	60
Foreign currency translation adjustments	0
Impact of settlements and curtailments	0
Net change	130
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss arising during the year	218
New prior service credit	2
Amortization of actuarial loss	71	$ 62	$ 63
Amortization of prior service credit	0
Foreign currency translation adjustments	9
Impact of settlements and curtailments	(5)
Net change	$ 153