Consolidated Statements of Changes in Equity - USD ($) $ in Millions	Total	Common Stock	Treasury Stock	APIC	Retained Earnings	AOCI
Beginning balance (in shares) at Dec. 31, 2023		46,767,164
Beginning balance at Dec. 31, 2023	$ 828.9	$ 0.5	$ (2,957.8)	$ 508.1	$ 3,278.1	$ 0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	66.0				66.0
Cash dividends declared	(8.8)				(8.8)
Dividend equivalent units accrued	0.0			0.1	(0.1)
Purchase of treasury stock	(86.9)		(86.9)
Issuance of treasury stock	(0.1)		11.0	(11.1)
Amounts related to share-based compensation	(23.1)			(23.1)
Share-based compensation expense	5.6			5.6
Ending balance (in shares) at Mar. 31, 2024		46,767,164
Ending balance at Mar. 31, 2024	781.6	$ 0.5	(3,033.7)	479.6	3,335.2	0.0
Beginning balance (in shares) at Dec. 31, 2023		46,767,164
Beginning balance at Dec. 31, 2023	828.9	$ 0.5	(2,957.8)	508.1	3,278.1	0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	210.8
Ending balance (in shares) at Jun. 30, 2024		46,767,164
Ending balance at Jun. 30, 2024	811.3	$ 0.5	(3,139.4)	479.3	3,470.9	0.0
Beginning balance (in shares) at Mar. 31, 2024		46,767,164
Beginning balance at Mar. 31, 2024	781.6	$ 0.5	(3,033.7)	479.6	3,335.2	0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	144.8				144.8
Cash dividends declared	(9.1)				(9.1)
Purchase of treasury stock	(107.1)		(107.1)
Issuance of treasury stock	0.1		1.4	(1.3)
Amounts related to share-based compensation	(4.1)			(4.1)
Share-based compensation expense	5.1			5.1
Ending balance (in shares) at Jun. 30, 2024		46,767,164
Ending balance at Jun. 30, 2024	$ 811.3	$ 0.5	(3,139.4)	479.3	3,470.9	0.0
Beginning balance (in shares) at Dec. 31, 2024	46,767,164	46,767,164
Beginning balance at Dec. 31, 2024	$ 840.1	$ 0.5	(3,391.3)	487.5	3,743.4	0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	53.2				53.2
Cash dividends declared	(9.8)				(9.8)
Dividend equivalent units accrued	0.0			0.1	(0.1)
Purchase of treasury stock	(151.2)		(151.2)
Issuance of treasury stock	0.0		8.4	(8.4)
Amounts related to share-based compensation	(18.6)			(18.6)
Share-based compensation expense	5.9			5.9
Ending balance (in shares) at Mar. 31, 2025		46,767,164
Ending balance at Mar. 31, 2025	$ 719.6	$ 0.5	(3,534.1)	466.5	3,786.7	0.0
Beginning balance (in shares) at Dec. 31, 2024	46,767,164	46,767,164
Beginning balance at Dec. 31, 2024	$ 840.1	$ 0.5	(3,391.3)	487.5	3,743.4	0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 198.8
Ending balance (in shares) at Jun. 30, 2025	46,767,164	46,767,164
Ending balance at Jun. 30, 2025	$ 646.1	$ 0.5	(3,745.9)	469.1	3,922.4	0.0
Beginning balance (in shares) at Mar. 31, 2025		46,767,164
Beginning balance at Mar. 31, 2025	719.6	$ 0.5	(3,534.1)	466.5	3,786.7	0.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	145.6				145.6
Cash dividends declared	(9.8)				(9.8)
Dividend equivalent units accrued	0.0			0.1	(0.1)
Purchase of treasury stock	(211.9)		(211.9)
Issuance of treasury stock	0.0		0.1	(0.1)
Amounts related to share-based compensation	(0.6)			(0.6)
Share-based compensation expense	$ 3.2			3.2
Ending balance (in shares) at Jun. 30, 2025	46,767,164	46,767,164
Ending balance at Jun. 30, 2025	$ 646.1	$ 0.5	$ (3,745.9)	$ 469.1	$ 3,922.4	$ 0.0