Retirement Benefit Plans - Changes in Plan Assets and Benefit Obligations in AOCL (Details) - Foreign Plan [Member] - Pension Plan [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in prior service cost recognized in accumulated other comprehensive loss:
Accumulated other comprehensive income (loss) at beginning of year	$ 0.5	$ 0.5
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0.0	0.0	$ 0.0
Recognized prior service credit (cost)	0.0	(0.1)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment	0.0	0.1	(0.6)
Total recognized in accumulated other comprehensive income at December 31	$ 0.5	$ 0.5	$ 0.5