CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Paid-in Capital	Retained Earnings	Other
Balance (in shares) at Dec. 31, 2019		52.9
Balance at Dec. 31, 2019	$ 1,376.2	$ 0.5	$ 638.0	$ 744.7	$ (7.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	32.4		32.4
Employee stock purchase plan (in shares)		0.8
Employee stock purchase plan	12.1	$ 0.0	12.1
Tax withholding on restricted stock vesting (in shares)		0.0
Tax withholding on restricted stock vesting	(12.0)		(12.0)
Stock repurchase and retirement of shares (in shares)		(0.8)
Stock repurchase and retirement of shares	(27.9)		(9.2)	(18.7)
Other	6.0				6.0
Net income	200.3			200.3
Balance (in shares) at Dec. 31, 2020		52.9
Balance at Dec. 31, 2020	1,587.1	$ 0.5	661.3	926.3	(1.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	52.7		52.7
Employee stock purchase plan (in shares)		0.5
Employee stock purchase plan	14.3	$ 0.0	14.3
Tax withholding on restricted stock vesting (in shares)		0.0
Tax withholding on restricted stock vesting	(16.0)		(16.0)
Stock repurchase and retirement of shares (in shares)		(1.6)
Stock repurchase and retirement of shares	(183.3)	$ 0.0	(21.5)	(161.8)
Other	0.7				0.7
Net income	409.9			409.9
Balance (in shares) at Dec. 31, 2021		51.8
Balance at Dec. 31, 2021	1,865.4	$ 0.5	690.8	1,174.4	(0.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	49.3		49.3
Employee stock purchase plan (in shares)		0.5
Employee stock purchase plan	18.9	$ 0.0	18.9
Tax withholding on restricted stock vesting (in shares)		0.0
Tax withholding on restricted stock vesting	(16.6)		(16.6)
Stock repurchase and retirement of shares (in shares)		(2.8)
Stock repurchase and retirement of shares	(281.4)	$ 0.0	(38.9)	(242.5)
Other	(2.4)				(2.4)
Net income	268.1			268.1
Balance (in shares) at Dec. 31, 2022		49.5
Balance at Dec. 31, 2022	$ 1,901.3	$ 0.5	$ 703.5	$ 1,200.0	$ (2.7)