XML 103 R87.htm IDEA: XBRL DOCUMENT v3.8.0.1
Employee plans - Schedule of Accumulated and Projected Benefit Obligation in Excess of Plan Assets (Details) - USD ($)
$ in Millions
Dec. 31, 2017
Dec. 31, 2016
Retirement Benefits [Abstract]    
Accumulated benefit obligation $ 7,151.7 $ 7,551.8
Fair value of plan assets 5,227.0 5,357.2
Projected benefit obligation 7,153.4 7,555.2
Fair value of plan assets $ 5,227.0 $ 5,357.2