Share-Based Compensation and Capital Stock Pre-Tax Stock-Based Compensation Expenses And Associated Income Tax Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-Based Compensation and Capital Stock [Line Items]
Share-based compensation expense	$ 14.0	$ 3.1	$ 21.7	$ 11.0
Income tax benefits	5.2	1.1	8.0	4.1
Stock options
Share-Based Compensation and Capital Stock [Line Items]
Share-based compensation expense	6.4	1.0	8.6	3.6
Restricted stock
Share-Based Compensation and Capital Stock [Line Items]
Share-based compensation expense	3.9	1.7	7.3	5.7
Performance Vested Restricted Stock Units
Share-Based Compensation and Capital Stock [Line Items]
Share-based compensation expense	$ 3.7	$ 0.4	$ 5.8	$ 1.7