Consolidated Statement Of Shareholders' Equity - USD ($) $ in Millions	Total	Preferred Stock	Common Stock	Treasury Stock	Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	As Reported	As Reported Preferred Stock	As Reported Common Stock	As Reported Treasury Stock	As Reported Paid-in Capital	As Reported Accumulated Deficit	As Reported Accumulated Other Comprehensive Loss	New Revenue Standard Adjustment	New Revenue Standard Adjustment Accumulated Deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2014-09															$ 1.9	$ 1.9
Beginning balance (in shares) at Dec. 31, 2015		0	168,200,000	0					0	168,200,000	0
Beginning balance at Dec. 31, 2015	$ 1,097.8	$ 0.0	$ 1.7	$ 0.0	$ 2,806.9	$ (1,649.7)	$ (61.1)	$ 1,095.9	$ 0.0	$ 1.7	$ 0.0	$ 2,806.9	$ (1,651.6)	$ (61.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 425.1					425.1		424.4
Net income | Accounting Standards Update 2014-09															0.7
Common stock issued for equity-based compensation (in shares)	200,000
Common stock issued for equity-based compensation	$ 0.0				0.0
Equity-based compensation expense	33.2				33.2
Stock option exercises (in shares)			400,000
Stock option exercises	7.4				7.4
Coworker Stock Purchase Plan (in shares)			200,000
Coworker Stock Purchase Plan	9.3				9.3
Repurchases of common stock (in shares)			(8,700,000)
Repurchases of common stock	(367.5)		$ (0.1)			(367.4)
Dividends paid	(78.7)				0.5	(79.2)
Foreign currency translation	(78.7)						(78.7)
Ending balance (in shares) at Dec. 31, 2016		0	160,300,000	0
Ending balance at Dec. 31, 2016	1,047.9	$ 0.0	$ 1.6	$ 0.0	2,857.3	(1,671.2)	(139.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	523.1					523.1		$ 523.0
Net income | Accounting Standards Update 2014-09															$ 0.1
Equity-based compensation expense	37.9				37.9
Stock option exercises (in shares)			1,500,000
Stock option exercises	13.0				13.0
Coworker Stock Purchase Plan (in shares)			200,000
Coworker Stock Purchase Plan	10.3				10.3
Repurchases of common stock (in shares)			(8,900,000)
Repurchases of common stock	(534.0)		$ (0.1)			(533.9)
Dividends paid	(106.9)				0.7	(107.6)
Incentive compensation plan stock withheld for taxes (in shares)				100,000
Incentive compensation plan stock withheld for taxes	(49.6)				(7.6)	(42.0)
Foreign currency translation	43.7
Unrealized loss from hedge accounting	0.2						0.2
Ending balance (in shares) at Dec. 31, 2017		0	153,100,000	100,000
Ending balance at Dec. 31, 2017	985.6	$ 0.0	$ 1.5	$ 0.0	2,911.6	(1,831.6)	(95.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	643.0					643.0
Equity-based compensation expense	$ 36.5				36.5
Stock option exercises (in shares)	935,250		800,000
Stock option exercises	$ 28.6				28.6
Coworker Stock Purchase Plan (in shares)			100,000
Coworker Stock Purchase Plan	11.8				11.8
Repurchases of common stock (in shares)			(6,300,000)
Repurchases of common stock	(522.3)					(522.3)
Dividends paid	(139.4)				0.8	(140.2)
Incentive compensation plan stock withheld for taxes (in shares)				(100,000)
Incentive compensation plan stock withheld for taxes	(33.9)				7.6	(41.5)
Foreign currency translation	(32.7)
Unrealized loss from hedge accounting	(2.0)						(2.0)
Ending balance (in shares) at Dec. 31, 2018		0	147,700,000	0
Ending balance at Dec. 31, 2018	$ 975.2	$ 0.0	$ 1.5	$ 0.0	$ 2,996.9	$ (1,892.6)	$ (130.6)