Earnings Per Share (Basic and Diluted) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income from continuing operations		$ 97.6	$ 107.8	$ 283.5	$ 316.1
Loss from discontinued operations, net of income taxes		(0.1)	(0.5)	(0.2)	(0.9)
NET INCOME		$ 97.5	$ 107.3	$ 283.3	$ 315.2
Weighted average common shares outstanding used in calculating basic EPS (in shares)		97.3	101.9	99.9	103.8
Effect of dilutive stock options and unvested RSUs (in shares)		0.4	0.7	0.4	0.7
Weighted average common shares outstanding used in calculating diluted EPS (in shares)		97.7	102.6	100.3	104.5
Basic EPS amounts(1):
Continuing operations (in dollars per share)	[1]	$ 1.00	$ 1.06	$ 2.84	$ 3.05
Discontinued operations (in dollars per share)	[1]	0.00	0.00	0.00	(0.01)
Net income (in dollars per share)	[1]	1.00	1.05	2.84	3.04
Diluted EPS amounts(1):
Continuing operations (in dollars per share)	[1]	1.00	1.05	2.83	3.02
Discontinued operations (in dollars per share)	[1]	0.00	0.00	0.00	(0.01)
Net income (in dollars per share)	[1]	$ 1.00	$ 1.05	$ 2.82	$ 3.02

[1] Earnings per share amounts are calculated discretely and therefore may not add up to the total due to rounding.