CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY/(DEFICIT) - USD ($) shares in Millions, $ in Millions	Common Stock	Capital Surplus	Accumulated Deficit	Accumulated Other Comprehensive Loss	Total
Beginning balance at Dec. 31, 2018	$ 4.4	$ 755.6	$ (838.8)	$ (231.0)	$ (309.8)
Beginning balance (shares) at Dec. 31, 2018	441.2
Increase/(Decrease) in Stockholders' Equity [Roll Forward]
Net income			173.1		173.1
Stock-based compensation		13.7			13.7
Common stock dividends and dividend equivalents declared			(87.4)		(87.4)
Repurchase and retirement of common shares	$ (0.1)		(184.9)		(185.0)
Repurchase and retirement of common shares (shares)	(10.2)
Shares issued under stock-based compensation plans		1.8			1.8
Shares issued under stock-based compensation plans (shares)	1.9
Other comprehensive income (Note 11)				19.4	19.4
Ending balance at Mar. 31, 2019	$ 4.3	771.1	(938.0)	(211.6)	(374.2)
Ending balance (shares) at Mar. 31, 2019	432.9
Beginning balance at Dec. 31, 2019	$ 4.2	841.2	(675.9)	(209.0)	$ (39.5)
Beginning balance (shares) at Dec. 31, 2019	418.0				418.0
Increase/(Decrease) in Stockholders' Equity [Roll Forward]
Net income			176.7		$ 176.7
Stock-based compensation		12.5			12.5
Common stock dividends and dividend equivalents declared			(93.3)		(93.3)
Repurchase and retirement of common shares	$ (0.1)		(235.1)		(235.2)
Repurchase and retirement of common shares (shares)	(9.2)
Shares issued under stock-based compensation plans		1.0			1.0
Shares issued under stock-based compensation plans (shares)	2.1
Other comprehensive income (Note 11)				28.7	28.7
Ending balance at Mar. 31, 2020	$ 4.1	$ 854.7	(828.2)	$ (180.3)	$ (149.7)
Ending balance (shares) at Mar. 31, 2020	410.9				410.9
Increase/(Decrease) in Stockholders' Equity [Roll Forward]
Adoption of new accounting pronouncements (Note 1)			$ (0.6)		$ (0.6)