Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Treasury Stock	Retained Earnings
Balance (in shares) at Dec. 31, 2022		72,700,000
Balance at Dec. 31, 2022	$ 4,796.7	$ 0.7	$ 2,388.4	$ (55.5)	$ (2,579.2)	$ 5,042.3
Increase (Decrease) in Stockholders' Equity
Net income	240.9					240.9
Foreign currency translation loss	0.0
Unrealized gain (Loss) on available-for-sale debt securities	19.9			19.9
Defined benefit pension plan	(3.2)			(3.2)
Shares issued under ESPP	3.4		3.4
Restricted stock units (RSUs) withheld for taxes	(13.5)		(13.5)
Common stock issued for RSUs vested (in shares)		100,000
Exercise of stock options (in shares)		500,000
Exercise of stock options	61.4		61.4
Share-based compensation	17.6		17.6
Balance (in shares) at Mar. 31, 2023		73,300,000
Balance at Mar. 31, 2023	$ 5,123.2	$ 0.7	2,457.3	(38.8)	(2,579.2)	5,283.2
Balance (in shares) at Dec. 31, 2023	73,659,761	73,700,000
Balance at Dec. 31, 2023	$ 5,984.8	$ 0.7	2,549.0	(12.8)	(2,579.2)	6,027.1
Increase (Decrease) in Stockholders' Equity
Net income	306.6
Foreign currency translation loss	2.4			2.4
Unrealized gain (Loss) on available-for-sale debt securities	(3.5)			(3.5)
Defined benefit pension plan	(1.7)			(1.7)
Shares issued under ESPP	3.9		3.9
Restricted stock units (RSUs) withheld for taxes	(11.4)		(11.4)
Share repurchase	(1,000.0)		(200.0)		(800.0)
Excise tax on net share repurchase	(6.9)				(6.9)
Common stock issued for RSUs vested (in shares)		100,000
Exercise of stock options (in shares)		300,000
Exercise of stock options	42.2		42.2
Share-based compensation	$ 21.7		21.7
Balance (in shares) at Mar. 31, 2024	74,098,932	74,100,000
Balance at Mar. 31, 2024	$ 5,338.1	$ 0.7	$ 2,405.4	$ (15.6)	$ (3,386.1)	$ 6,333.7