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Pension Plans, Other Postretirement Benefits, and Defined-Contribution Plans - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Retirement Benefits [Abstract]      
Defined-benefit plan, amortization of net actuarial loss in 2019 $ 12,000,000    
Defined benefit plan, amortization of prior service credit in 2019 $ 2,000,000    
Defined benefit plan, annual rate of increase assumed for next fiscal year 1.70% 2.00% 2.00%
Defined Benefit Plan Disclosure [Line Items]      
Defined benefit plan, amount of employer securities included in plan assets $ 0    
Defined-contribution plans, recognized expense $ 63,000,000 $ 63,000,000 $ 64,000,000
Maximum [Member] | Equity Securities [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined benefit plan, target asset-allocation percentages 0.5    
Maximum [Member] | Fixed Income [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined benefit plan, target asset-allocation percentages 0.25    
Maximum [Member] | Other Investments [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Defined benefit plan, target asset-allocation percentages 0.25