XML 110 R96.htm IDEA: XBRL DOCUMENT v3.10.0.1
Defined Benefit Plans - Assumed Health Care Cost Trend Rates Used to Determine Benefit Obligations and Net Cost (Detail)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Aug. 31, 2018
Defined Benefit Plan Disclosure [Line Items]      
Health care cost trend rate assumed for next year     1.00%
Postretirement Benefits [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Rate that the cost trend rate is assumed to decline (the ultimate trend rate) 4.50% 4.50%  
Year that the rate reaches the ultimate trend rate 2027 2026  
Postretirement Benefits [Member] | Pre Age Sixty Five      
Defined Benefit Plan Disclosure [Line Items]      
Health care cost trend rate assumed for next year [1] 6.90% 7.10%  
Postretirement Benefits [Member] | Post Age Sixty Five      
Defined Benefit Plan Disclosure [Line Items]      
Health care cost trend rate assumed for next year [1] 8.00% 8.40%  
[1] The pre-65 initial health care cost trend rate is shown first / followed by the post-65 rate.