XML 111 R92.htm IDEA: XBRL DOCUMENT v3.8.0.1
Components of Net Periodic Postretirement Health Care Costs (Parenthetical) (Detail) - Postretirement Benefit Plans - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]        
Pension curtailment gain $ 9      
Net loss from experience differences $ 10 $ (14) $ (10) $ (13)
Prior service credit [1]   $ (40) $ (20) $ (7)
[1] In the fourth quarter of 2016, the prior service credit included a one-time $9 million curtailment gain related to a change in the eligibility requirement resulting in ongoing amortization of $10 million. In 2017, we continue to amortize prior service credit and recorded $40 million on a full year basis.