Summary of Pre-Tax Expense Associated with Fair value of Unvested Stock Options and Restricted Stock Awards (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock compensation expense	$ 15.7	$ 14.4	$ 14.8
Cost of Sales
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock compensation expense	1.8	1.9	1.6
Selling, General and Administrative Expenses
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock compensation expense	16.3	14.1	14.5
Unvested Stock Options Fair Value
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock compensation expense	$ 18.1	$ 16.0	$ 16.1