Share-Based Compensation and Capital Stock Pre-Tax Stock-Based Compensation Expenses And Associated Income Tax Benefits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Share-Based Compensation and Capital Stock [Line Items]
Share-based compensation expense	$ (4.4)	$ (2.9)	$ (7.9)	$ (5.7)
Income tax benefits	1.6	1.1	2.9	2.1
Stock options
Share-Based Compensation and Capital Stock [Line Items]
Share-based compensation expense	(1.5)	(0.9)	(2.6)	(1.6)
Restricted stock
Share-Based Compensation and Capital Stock [Line Items]
Share-based compensation expense	(2.2)	(1.7)	(4.0)	(3.5)
Performance Vested Restricted Stock Units
Share-Based Compensation and Capital Stock [Line Items]
Share-based compensation expense	$ (0.7)	$ (0.3)	$ (1.3)	$ (0.6)