Employee Benefit Plans (Weighted Average Assumptions Used to Determine Benefit Obligation for Defined Benefit Pension and Other Postretirement Plans) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Return on plan assets assumption	5.40%	6.10%	6.10%
Impact on Net Periodic Pension Expense - Next Twelve Months	$ 11
Discount rate used to calculate benefit obligation	3.20%	3.70%
Rate of compensation increase	1.30%	1.60%
Pensions
Defined Benefit Plan Disclosure [Line Items]
Impact on Net Periodic Pension Expense - Next Twelve Months	$ 22
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Impact on Net Periodic Pension Expense - Next Twelve Months	$ 26
UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Discount rate used to calculate benefit obligation	3.70%	4.30%