XML 117 R100.htm IDEA: XBRL DOCUMENT v3.8.0.1
Pension and Other Benefit Plans - Effect of One Percentage Point Change in Assumed Health Care Cost Trend Rates (Detail) - Postretirement medical plan
$ in Millions
12 Months Ended
Dec. 31, 2017
USD ($)
Defined Benefit Plan Disclosure [Line Items]  
Effect on total service and interest cost components, One Percentage Point Decrease $ (3)
Effect on accumulated postretirement benefit obligation, One Percentage Point Decrease (30)
United States  
Defined Benefit Plan Disclosure [Line Items]  
Effect on total service and interest cost components, One Percentage Point Increase 3
Effect on accumulated postretirement benefit obligation, One Percentage Point Increase $ 35