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, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain) arising during the year	$ 3
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain) arising during the year	(35)
New prior service cost (credit)	1
Amortization of actuarial loss	12	$ 19	$ 32
Amortization of prior service (cost) credit	59	31	9
Foreign currency translation adjustments	0
Impact of settlements and curtailments	0
Net change	13
Pensions
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain) arising during the year	38
New prior service cost (credit)	(2)
Amortization of actuarial loss	75	110	119
Amortization of prior service (cost) credit	(1)	$ 1	$ 2
Foreign currency translation adjustments	19
Impact of settlements and curtailments	(63)
Net change	$ (84)