Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock, Common
BALANCE, Shares at Dec. 31, 2020		102,562,149
BALANCE, Amount at Dec. 31, 2020	$ 3,235.7	$ 1.0	$ 53.1	$ 4,069.4	$ (887.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,373.0			1,373.0
Repurchases of common stock	(2,303.2)				(2,303.2)
Treasury stock cancellation, Shares		(16,000,000)
Treasury stock cancellation	0.0	$ (0.2)	(40.6)	(797.2)	838.0
Stock-based compensation expense	35.0		35.0
Shares awarded under stock-based compensation plans, net of shares withheld for taxes	36.5		(44.3)	(5.3)	86.1
BALANCE, Shares at Dec. 31, 2021		86,562,149
BALANCE, Amount at Dec. 31, 2021	2,377.0	$ 0.8	3.2	4,639.9	(2,266.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,377.4			1,377.4
Repurchases of common stock	(1,710.2)				(1,710.2)
Treasury stock cancellation, Shares		(23,000,000)
Treasury stock cancellation	0.0	$ (0.2)	(7.8)	(2,295.5)	2,303.5
Stock-based compensation expense	31.5		31.5
Shares awarded under stock-based compensation plans, net of shares withheld for taxes	(27.9)		(23.8)	(58.1)	54.0
BALANCE, Shares at Dec. 31, 2022		63,562,149
BALANCE, Amount at Dec. 31, 2022	2,047.8	$ 0.6	3.1	3,663.7	(1,619.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,021.1			1,021.1
Repurchases of common stock	(871.7)				(871.7)
Stock-based compensation expense	39.7		39.7
Shares awarded under stock-based compensation plans, net of shares withheld for taxes	(25.5)		(20.4)	(41.8)	36.7
BALANCE, Shares at Dec. 31, 2023		63,562,149
BALANCE, Amount at Dec. 31, 2023	$ 2,211.4	$ 0.6	$ 22.4	$ 4,643.0	$ (2,454.6)