Retirement Benefits - Information Comparing Plan Assets to Plan Obligations (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Total
Information for pension plans with an ABO in excess of plan assets:
Fair value of plan assets	$ 731.5	$ 824.8
Accumulated benefit obligation	906.5	1,010.5
Projected benefit obligation	921.6	1,030.1
U.S. Plans
Information for pension plans with an ABO in excess of plan assets:
Fair value of plan assets	686.6	777.2
Accumulated benefit obligation	801.9	890.3
Projected benefit obligation	801.9	890.3
Non-U.S. Plans
Information for pension plans with an ABO in excess of plan assets:
Fair value of plan assets	44.9	47.6
Accumulated benefit obligation	104.6	120.2
Projected benefit obligation	$ 119.7	$ 139.8