Share-Based Compensation and Equity - Share-based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Pre-tax compensation expense	$ 36.6	$ 33.9	$ 22.2
Tax benefit	(8.2)	(8.3)	(7.0)
Stock option expense, net of tax	28.4	25.6	15.2
Stock Options [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Pre-tax compensation expense	2.8	4.6	2.7
Tax benefit	(0.6)	(1.3)	(0.9)
Stock option expense, net of tax	2.2	3.3	1.8
Restricted Stock Units [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Pre-tax compensation expense	19.8	16.4	10.7
Tax benefit	(4.3)	(4.0)	(3.1)
Stock option expense, net of tax	15.5	12.4	7.6
Performance Shares [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Pre-tax compensation expense	14.0	12.9	8.8
Tax benefit	(3.3)	(3.0)	(3.0)
Stock option expense, net of tax	$ 10.7	$ 9.9	$ 5.8