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Post-Employment and Other Long-Term Employees Benefits - Components of Net Periodic Benefit Cost (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Pension Benefits [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Service cost $ 27 $ 27 $ 28
Interest cost 23 25 25
Expected return on plan assets (21) (20) (22)
Amortization of actuarial net loss (gain) 9 8 7
Amortization of prior service cost   1 1
Effect of settlement 1   1
Net periodic benefit cost 39 41 40
Other Long-Term Benefit [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 3 3 5
Interest cost 2 2 2
Amortization of actuarial net loss (gain) 3    
Effect of curtailment   (1) (1)
Net periodic benefit cost $ 8 $ 4 $ 6