Pension and Other Post-Retirement Plans - Fair Value of Plan Assets (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
U.K. Plan
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	$ 63.7	$ 62.6
U.K. Plan | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	0.3	0.4
U.K. Plan | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	50.9	50.4
U.K. Plan | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	12.5	11.8	10.4
U.K. Plan | Global return fund
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	19.3	19.4
U.K. Plan | Global return fund | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	19.3	19.4
U.K. Plan | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	6.1	5.4
U.K. Plan | Corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	6.1	5.4
U.K. Plan | Real estate
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	12.5	11.8
U.K. Plan | Real estate | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	12.5	11.8
U.K. Plan | Cash
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	0.3	0.4
U.K. Plan | Cash | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	0.3	0.4
U.K. Plan | U.K | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	15.2	16.0
U.K. Plan | U.K | Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	15.2	16.0
U.K. Plan | Other foreign countries | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	10.3	9.6
U.K. Plan | Other foreign countries | Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	10.3	9.6
Canadian Plan
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	42.9	40.8
Canadian Plan | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	26.7	27.0
Canadian Plan | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	16.2	13.8
Canadian Plan | Government bonds
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	6.5	5.8
Canadian Plan | Government bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	6.5	5.8
Canadian Plan | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total pension assets		8.0
Canadian Plan | Corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total pension assets		8.0
Canadian Plan | Other short-term investment
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	0.4	0.6
Canadian Plan | Other short-term investment | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	0.4	0.6
Canadian Plan | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	0.3	0.2
Canadian Plan | Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	0.3	0.2
Canadian Plan | Canada | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	7.9	8.0
Canadian Plan | Canada | Equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	7.3	8.0
Canadian Plan | Canada | Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	0.6
Canadian Plan | Canada | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	9.1
Canadian Plan | Canada | Corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	9.1
Canadian Plan | Other foreign countries | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	18.7	18.2
Canadian Plan | Other foreign countries | Equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total pension assets	$ 18.7	$ 18.2