CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY/(DEFICIT) - USD ($) shares in Millions, $ in Millions	Adoption of new accounting pronouncements Accumulated Deficit	Adoption of new accounting pronouncements Accumulated Other Comprehensive Loss	Adoption of new accounting pronouncements	Common Stock	Capital Surplus	Accumulated Deficit	Accumulated Other Comprehensive Loss	Total
Beginning balance at Dec. 31, 2017	$ 30.7	$ (31.4)	$ (0.7)	$ 4.6	$ 697.8	$ (965.9)	$ (227.9)	$ (491.4)
Beginning balance (shares) at Dec. 31, 2017				459.0
Increase/(Decrease) in Stockholders' Equity [Roll Forward]
Net income						851.9		851.9
Stock-based compensation					47.7			47.7
Common stock dividends and dividend equivalents declared						(341.7)		(341.7)
Repurchase and retirement of common shares				$ (0.2)		(413.8)		(414.0)
Repurchase and retirement of common shares (shares)				(20.9)
Shares issued under stock-based compensation plans					10.1			10.1
Shares issued under stock-based compensation plans (shares)				3.1
Other comprehensive income (Note 14)							28.3	28.3
Ending balance at Dec. 31, 2018				$ 4.4	755.6	(838.8)	(231.0)	(309.8)
Ending balance (shares) at Dec. 31, 2018				441.2
Increase/(Decrease) in Stockholders' Equity [Roll Forward]
Net income						1,058.3		1,058.3
Stock-based compensation					48.9			48.9
Common stock dividends and dividend equivalents declared						(342.6)		(342.6)
Repurchase and retirement of common shares				$ (0.2)		(552.8)		(553.0)
Repurchase and retirement of common shares (shares)				(27.6)
Shares issued under stock-based compensation plans					36.7			36.7
Shares issued under stock-based compensation plans (shares)				4.4
Other comprehensive income (Note 14)							22.0	22.0
Ending balance at Dec. 31, 2019	$ (0.6)		$ (0.6)	$ 4.2	841.2	(675.9)	(209.0)	$ (39.5)
Ending balance (shares) at Dec. 31, 2019				418.0				418.0
Increase/(Decrease) in Stockholders' Equity [Roll Forward]
Net income						744.3		$ 744.3
Stock-based compensation					41.7			41.7
Common stock dividends and dividend equivalents declared						(373.2)		(373.2)
Repurchase and retirement of common shares				$ (0.1)		(237.7)		(237.8)
Repurchase and retirement of common shares (shares)				(9.4)
Shares issued under stock-based compensation plans					2.2			2.2
Shares issued under stock-based compensation plans (shares)				2.6
Other comprehensive income (Note 14)							49.5	49.5
Ending balance at Dec. 31, 2020				$ 4.1	$ 885.1	$ (543.1)	$ (159.5)	$ 186.6
Ending balance (shares) at Dec. 31, 2020				411.2				411.2