Retirement Benefit Plans - Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Amounts recognized on the Consolidated Balance Sheets:
Non-current assets	$ 19.7	$ 32.1
Pension Plan [Member]
Amounts recognized on the Consolidated Balance Sheets:
Current liabilities	6.4	5.7
Domestic Plan [Member] | Pension Plan [Member]
Amounts recognized on the Consolidated Balance Sheets:
Non-current assets	6.7	26.4
Current liabilities	4.8	4.3
Non-current liabilities	(113.0)	(104.9)
Total	(111.1)	(82.8)
Foreign Plan [Member] | Pension Plan [Member]
Amounts recognized on the Consolidated Balance Sheets:
Non-current assets	13.0	5.7
Current liabilities	1.5	1.4
Non-current liabilities	(54.3)	(49.8)
Total	$ (42.8)	$ (45.5)