XML 53 R37.htm IDEA: XBRL DOCUMENT v3.8.0.1
Components of Net Periodic Benefit Cost (Detail) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Pension Benefits    
Defined Benefit Plan Disclosure [Line Items]    
Service cost $ 57 $ 49
Interest cost 54 55
Expected return on plan assets (73) (60)
Amortization of unrecognized (gain) loss and prior service cost (credit) 33 31
Settlement loss   1
Total 71 76
Other Postretirement Benefits    
Defined Benefit Plan Disclosure [Line Items]    
Service cost 3 2
Interest cost 15 17
Amortization of unrecognized (gain) loss and prior service cost (credit) (17) (18)
Total $ 1 $ 1