Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Taxes
Effective tax rate (as a percent)	27.10%	26.50%	26.80%	26.50%
Effective tax rate excluding the net impact of acquisition-related expenses (as a percent)	26.50%	26.50%	26.50%	26.50%
Liability for unrecognized tax benefits, which if recognized would impact the effective tax rate	$ 19.3		$ 19.3
Unrecognized tax benefits, anticipated adjustment for changing facts and circumstances, over the next twelve month period	$ 1.5		$ 1.5