Retirement Benefits - Pension Plan Weighted Average Asset Allocations (Details) - Pension Benefit Plan	Dec. 31, 2017	Dec. 31, 2016
U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan securities	100.00%	100.00%
U.S. Plans | Equity Securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan securities	47.00%	44.00%
U.S. Plans | Fixed Income Securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan securities	51.00%	43.00%
U.S. Plans | Cash/Commingled Funds/Other
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan securities	2.00%	13.00%
Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan securities	100.00%	100.00%
Non-U.S. Plans | Equity Securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan securities	14.00%	24.00%
Non-U.S. Plans | Fixed Income Securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan securities	30.00%	26.00%
Non-U.S. Plans | Cash/Commingled Funds/Other
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan securities	56.00%	50.00%