Pension and Other Post-Retirement Plans - Change in Level 3 Plan Assets (Details) (U.K. Plan, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Change in fair value of the pension assets valued using significant unobservable inputs (Level 3)
Fair value of assets at end of year	$ 63.7	$ 62.6
Level 3
Change in fair value of the pension assets valued using significant unobservable inputs (Level 3)
Fair value of plan assets at beginning of year	11.8	10.4
Purchases	0.1	0.1
Unrealized gain on asset still held, at end of year	0.6	1.3
Fair value of assets at end of year	$ 12.5	$ 11.8