Consolidated Statement Of Shareholders' Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Treasury Stock	Paid-in Capital	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2017			153,100,000	100,000
Beginning balance at Dec. 31, 2017	$ 985.6		$ 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)			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)
Dividend payments	(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)							(32.7)
Unrealized loss from hedge accounting	(5.9)							(5.9)
Reclassification of hedge accounting loss to net income	3.9							3.9
Ending balance (in shares) at Dec. 31, 2018			147,700,000	0
Ending balance at Dec. 31, 2018	975.2		$ 1.5	$ 0.0	2,996.9	(1,892.6)		(130.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	736.8					736.8
Equity-based compensation expense	47.7				47.7
Stock option exercises (in shares)			1,300,000
Stock option exercises	34.9				34.9
Coworker Stock Purchase Plan (in shares)			100,000
Coworker Stock Purchase Plan	14.9				14.9
Repurchases of common stock (in shares)			(6,100,000)
Repurchases of common stock	(657.2)		$ (0.1)			(657.1)
Dividend payments	(183.4)				0.9	(184.3)
Incentive compensation plan stock withheld for taxes	(21.4)					(21.4)
Foreign currency translation	22.4
Unrealized loss from hedge accounting	(11.3)							(11.3)
Reclassification of hedge accounting loss to net income	1.7							1.7
Ending balance (in shares) at Dec. 31, 2019			143,000,000.0	0
Ending balance at Dec. 31, 2019	960.3	$ 0.5	$ 1.4	$ 0.0	3,095.3	(2,018.6)	$ 0.5	(117.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	788.5					788.5
Equity-based compensation expense	$ 42.5				42.5
Stock option exercises (in shares)	1,119,812		1,400,000
Stock option exercises	$ 49.2				49.2
Coworker Stock Purchase Plan (in shares)			100,000
Coworker Stock Purchase Plan	16.8				16.8
Repurchases of common stock (in shares)			(2,600,000)
Repurchases of common stock	(340.6)					(340.6)
Dividend payments	(219.6)				1.1	(220.7)
Incentive compensation plan stock withheld for taxes	(22.5)					(22.5)
Foreign currency translation	16.6							16.6
Unrealized loss from hedge accounting	(0.6)							(0.6)
Reclassification of hedge accounting loss to net income	6.0							6.0
Ending balance (in shares) at Dec. 31, 2020			141,900,000	0
Ending balance at Dec. 31, 2020	$ 1,297.1		$ 1.4	$ 0.0	$ 3,204.9	$ (1,813.4)		$ (95.8)