Retirement Benefit Plans (Actual Allocation Percentage and Target Allocation Percentage for the U.S. Pension Plan Assets) (Details) - Pension Plan	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	47.20%	46.40%
Non-U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	21.10%	19.60%
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	31.40%	33.60%
Money market
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	0.30%	0.40%
Minimum | U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	0.36
Minimum | Non-U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	0.16
Minimum | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	0.3
Minimum | Money market
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	0
Maximum | U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	0.54
Maximum | Non-U.S. equity securities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	0.24
Maximum | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	0.4
Maximum | Money market
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Allocation Percentage	0.1