Retirement Benefit Plans (Changes in defined benefit plan obligations) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Actuarial (gains)/losses	$ 29.8	$ (7.0)	$ 4.8
Retirement Plans [Member]
Benefit obligation, beginning balance	486.2	426.7
Service cost	4.9	4.4	4.5
Interest cost	21.0	19.0	19.6
Contributions from plan participants	0	0
Actuarial (gains)/losses	51.1	32.6
Exchange difference	(35.0)	12.1
Benefits paid	(8.0)	(8.6)
Defined Benefit Plan, Plan Amendments	0	0
Curtailment	0	0
Benefit obligation, ending balance	520.2	486.2	426.7
Medical Plan [Member]
Benefit obligation, beginning balance	43.6	53.2
Service cost	0	0.2	0.3
Interest cost	1.8	1.9	2.1
Contributions from plan participants	0.4	0.5
Actuarial (gains)/losses	(9.2)	(8.9)
Exchange difference	0	0
Benefits paid	(2.9)	(1.8)
Defined Benefit Plan, Plan Amendments	(23.5)	0
Curtailment	0	(1.5)
Benefit obligation, ending balance	$ 10.2	$ 43.6	$ 53.2