Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Millions		Total	Common Stock Outstanding	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Shares in Treasury
Balance at the beginning of the period at Dec. 31, 2018		$ 2,597.4	$ 78.7	$ 391.8	$ (122.1)	$ 3,351.4	$ (1,102.4)
Balance (in shares) at Dec. 31, 2018			57,900				20,500
Increase (Decrease) in Shareholders' Equity
Net income		472.8				472.8
Other comprehensive income (loss), net of tax		(2.0)			(2.0)
Dividends		(102.9)				(102.9)
Repurchases of common stock		(374.9)					$ (374.9)
Repurchase of common stock (in shares)			(2,800)				2,800
Issuance and deferrals, net for stock based compensation	[1]	52.4		24.8			$ 27.6
Issuance and deferrals, net for stock-based compensation (in shares)	[1]		600				(600)
Balance at the end of the period at Dec. 31, 2019		2,642.8	$ 78.7	416.6	(124.1)	3,721.3	$ (1,449.7)
Balance (in shares) at Dec. 31, 2019			55,700				22,700
Increase (Decrease) in Shareholders' Equity
Net income		320.1				320.1
Other comprehensive income (loss), net of tax		27.1			27.1
Dividends		(112.7)				(112.7)
Repurchases of common stock		(382.4)					$ (382.4)
Repurchase of common stock (in shares)			(3,100)				3,100
Issuance and deferrals, net for stock based compensation	[1]	42.8		25.1			$ 17.7
Issuance and deferrals, net for stock-based compensation (in shares)	[1]		300				(300)
Balance at the end of the period at Dec. 31, 2020		2,537.7	$ 78.7	441.7	(97.0)	3,928.7	$ (1,814.4)
Balance (in shares) at Dec. 31, 2020			52,900				25,500
Increase (Decrease) in Shareholders' Equity
Net income		421.7				421.7
Other comprehensive income (loss), net of tax		(8.2)			(8.2)
Dividends		(112.7)				(112.7)
Repurchases of common stock		(315.6)					$ (315.6)
Repurchase of common stock (in shares)			(1,900)				1,900
Issuance and deferrals, net for stock based compensation	[1]	106.6		39.8			$ 66.8
Issuance and deferrals, net for stock-based compensation (in shares)	[1]		1,000				(1,000)
Balance at the end of the period at Dec. 31, 2021		$ 2,629.5	$ 78.7	$ 481.5	$ (105.2)	$ 4,237.7	$ (2,063.2)
Balance (in shares) at Dec. 31, 2021			52,000				26,400

[1] Issuances and deferrals, net for stock-based compensation reflects share activity related to option exercises, net of tax, restricted and performance shares vested, and net issuances and deferrals associated with deferred compensation equity.