Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Line Items]
Income before income taxes	$ 66.0	$ 89.1	$ 53.6	$ 147.8
Provision for income taxes	(36.1)	(25.4)	(28.0)	(34.2)
US domestic taxes would be incurred if repatriated to the United States	7.4		7.4
Cash and dash equivalents	992.6	$ 599.7	992.6	$ 599.7	$ 937.7	$ 178.2
United Kingdom and Ireland [Member]
Income Taxes [Line Items]
Cash and dash equivalents	$ 776.4		$ 776.4
U.S. Federal [Member]
Income Taxes [Line Items]
Federal statutory rate			35.00%