Retirement Benefit Plans (Schedule of fair value of plan assets by three level fair value hierarchy) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined benefit plan, fair value of plan assets	$ 424.0	$ 413.0
Cash and Cash Equivalents [Member]
Defined benefit plan, fair value of plan assets	7.2	0.2
Fund Investments [Member]
Defined benefit plan, fair value of plan assets	197.5	202.8
Equity Securities [Member]
Defined benefit plan, fair value of plan assets	124.8	122.8
Government Debt Securities [Member]
Defined benefit plan, fair value of plan assets	76.5	65.6
Other Assets [Member]
Defined benefit plan, fair value of plan assets	4.9	6.4
Guaranteed Investments Contracts [Member]
Defined benefit plan, fair value of plan assets	13.1	15.2
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined benefit plan, fair value of plan assets	349.6	344.9
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Cash and Cash Equivalents [Member]
Defined benefit plan, fair value of plan assets	7.2	0.2
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fund Investments [Member]
Defined benefit plan, fair value of plan assets	197.5	202.8
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Securities [Member]
Defined benefit plan, fair value of plan assets	124.8	122.8
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Government Debt Securities [Member]
Defined benefit plan, fair value of plan assets	15.2	12.7
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Assets [Member]
Defined benefit plan, fair value of plan assets	4.9	6.4
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Guaranteed Investments Contracts [Member]
Defined benefit plan, fair value of plan assets	0	0
Significant Other Observable Inputs (Level 2) [Member]
Defined benefit plan, fair value of plan assets	61.3	52.9
Significant Other Observable Inputs (Level 2) [Member] | Cash and Cash Equivalents [Member]
Defined benefit plan, fair value of plan assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Fund Investments [Member]
Defined benefit plan, fair value of plan assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Equity Securities [Member]
Defined benefit plan, fair value of plan assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Government Debt Securities [Member]
Defined benefit plan, fair value of plan assets	61.3	52.9
Significant Other Observable Inputs (Level 2) [Member] | Other Assets [Member]
Defined benefit plan, fair value of plan assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Guaranteed Investments Contracts [Member]
Defined benefit plan, fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) [Member]
Defined benefit plan, fair value of plan assets	13.1	15.2	14.8
Significant Unobservable Inputs (Level 3) [Member] | Cash and Cash Equivalents [Member]
Defined benefit plan, fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Fund Investments [Member]
Defined benefit plan, fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member]
Defined benefit plan, fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Government Debt Securities [Member]
Defined benefit plan, fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Other Assets [Member]
Defined benefit plan, fair value of plan assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Guaranteed Investments Contracts [Member]
Defined benefit plan, fair value of plan assets	$ 13.1	$ 15.2