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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-Based Compensation and Capital Stock [Line Items]
Share-based compensation expense	$ 3.1	$ 3.4	$ 11.0	$ 9.1
Income tax benefits	1.1	1.3	4.1	3.4
Stock options
Share-Based Compensation and Capital Stock [Line Items]
Share-based compensation expense	1.0	0.8	3.6	2.4
Restricted stock
Share-Based Compensation and Capital Stock [Line Items]
Share-based compensation expense	1.7	1.6	5.7	5.1
Performance Vested Restricted Stock Units
Share-Based Compensation and Capital Stock [Line Items]
Share-based compensation expense	$ 0.4	$ 1.0	$ 1.7	$ 1.6