Consolidated Statement of Shareholders' Equity (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2017		153.1
Beginning balance at Dec. 31, 2017	$ 985.6	$ 1.5	$ 2,911.6	$ (1,831.6)	$ (95.9)
Shareholders' Equity (Deficit) [Roll Forward]
Net income	300.0			300.0
Equity-based compensation expense	16.1		16.1
Stock option exercises (in shares)		0.7
Stock option exercises	19.9		19.9
Coworker Stock Purchase Plan (in shares)		0.1
Coworker stock purchase plan	5.4		5.4
Repurchases of common stock (in shares)		(2.4)
Repurchases of common stock	(176.4)			(176.4)
Dividends paid	(63.8)		0.3	(64.1)
Incentive compensation plan stock withheld for taxes	(8.7)			(8.7)
Foreign currency translation	(14.7)				(14.7)
Unrealized (loss) gain from hedge accounting	4.1				4.1
Realized gain from hedge accounting	1.4				1.4
Ending balance (in shares) at Jun. 30, 2018		151.5
Ending balance at Jun. 30, 2018	1,068.9	$ 1.5	2,953.3	(1,780.8)	(105.1)
Beginning balance (in shares) at Mar. 31, 2018		151.9
Beginning balance at Mar. 31, 2018	996.9	$ 1.5	2,928.5	(1,854.6)	(78.5)
Shareholders' Equity (Deficit) [Roll Forward]
Net income	173.0			173.0
Equity-based compensation expense	9.0		9.0
Stock option exercises (in shares)		0.4
Stock option exercises	12.6		12.6
Coworker Stock Purchase Plan (in shares)		0.1
Coworker stock purchase plan	3.0		3.0
Repurchases of common stock (in shares)		(0.9)
Repurchases of common stock	(67.2)			(67.2)
Dividends paid	(31.8)		0.2	(32.0)
Foreign currency translation	(28.9)				(28.9)
Unrealized (loss) gain from hedge accounting	1.4				1.4
Realized gain from hedge accounting	0.9				0.9
Ending balance (in shares) at Jun. 30, 2018		151.5
Ending balance at Jun. 30, 2018	1,068.9	$ 1.5	2,953.3	(1,780.8)	(105.1)
Beginning balance (in shares) at Dec. 31, 2018		147.7
Beginning balance at Dec. 31, 2018	975.2	$ 1.5	2,996.9	(1,892.6)	(130.6)
Shareholders' Equity (Deficit) [Roll Forward]
Net income	349.5			349.5
Equity-based compensation expense	24.0		24.0
Stock option exercises (in shares)		0.7
Stock option exercises	19.0		19.0
Coworker stock purchase plan	7.3		7.3
Repurchases of common stock (in shares)		(3.4)
Repurchases of common stock	(332.2)			(332.2)
Dividends paid	(86.3)		0.4	(86.7)
Incentive compensation plan stock withheld for taxes	(11.6)			(11.6)
Foreign currency translation	1.9				1.9
Unrealized (loss) gain from hedge accounting	(12.4)				(12.4)
Realized gain from hedge accounting	1.7				1.7
Ending balance (in shares) at Jun. 30, 2019		145.0
Ending balance at Jun. 30, 2019	936.1	$ 1.5	3,047.6	(1,973.6)	(139.4)
Beginning balance (in shares) at Mar. 31, 2019		146.3
Beginning balance at Mar. 31, 2019	927.3	$ 1.5	3,025.3	(1,972.0)	(127.5)
Shareholders' Equity (Deficit) [Roll Forward]
Net income	196.6			196.6
Equity-based compensation expense	11.8		11.8
Stock option exercises (in shares)		0.2
Stock option exercises	6.0		6.0
Coworker stock purchase plan	4.3		4.3
Repurchases of common stock (in shares)		(1.5)
Repurchases of common stock	(155.1)			(155.1)
Dividends paid	(42.9)		0.2	(43.1)
Foreign currency translation	(8.0)				(8.0)
Unrealized (loss) gain from hedge accounting	(4.1)				(4.1)
Realized gain from hedge accounting	0.2				0.2
Ending balance (in shares) at Jun. 30, 2019		145.0
Ending balance at Jun. 30, 2019	$ 936.1	$ 1.5	$ 3,047.6	$ (1,973.6)	$ (139.4)