XML 108 R92.htm IDEA: XBRL DOCUMENT v3.8.0.1
Employee plans - Assumed Health Care Cost Trend Rates (Details)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Retirement Benefits [Abstract]    
Health care cost trend rate assumed for next year 6.60% 5.80%
Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) 4.80% 4.80%
Year that the rate reaches the ultimate trend rate 2023 2023