Consolidated Statements of Changes in Shareholders' Equity Statement - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Treasury Stock, Common
Common stock, shares issued, beginning at Dec. 31, 2023		68,800,000
Treasury stock, shares issued, beginning at Dec. 31, 2023						33,300,000
Beginning balance at Dec. 31, 2023		$ 42.5	$ 816.1	$ 3,009.5	$ (167.6)	$ 1,427.5
Stock Issued During Period, Shares, New Issues		200,000
Stock Issued During Period, Value, New Issues		$ 0.2
Stock Repurchased During Period, Shares						(200,000)
APIC, Share-based Payment Arrangement, Increase for Cost Recognition			24.8
Net income	$ 207.7			207.7
Dividends declared (in dollars per share)	$ 1.74
Dividends, Common Stock, Cash				(64.2)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ (17.0)				(17.0)
Common stock, shares issued, ending at Sep. 30, 2024		69,000,000.0
Treasury stock, shares issued, ending at Sep. 30, 2024						33,500,000
Ending balance at Sep. 30, 2024	2,436.7	$ 42.7	840.9	3,153.0	(150.6)	$ 1,449.3
Stock repurchases	(21.8)					$ (21.8)
Common stock, shares issued, beginning at Jun. 30, 2024		69,000,000.0
Treasury stock, shares issued, beginning at Jun. 30, 2024						33,400,000
Beginning balance at Jun. 30, 2024		$ 42.7	836.4	3,085.4	(184.8)	$ 1,436.3
Stock Issued During Period, Shares, New Issues		0
Stock Issued During Period, Value, New Issues		$ 0.0
Stock Repurchased During Period, Shares						(100,000)
APIC, Share-based Payment Arrangement, Increase for Cost Recognition			4.5
Net income	$ 89.0			89.0
Dividends declared (in dollars per share)	$ 0.58
Dividends, Common Stock, Cash				(21.4)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ (34.2)				(34.2)
Common stock, shares issued, ending at Sep. 30, 2024		69,000,000.0
Treasury stock, shares issued, ending at Sep. 30, 2024						33,500,000
Ending balance at Sep. 30, 2024	$ 2,436.7	$ 42.7	840.9	3,153.0	(150.6)	$ 1,449.3
Stock repurchases						$ (13.0)
Common stock, shares issued, beginning at Dec. 31, 2024	69,075,329	69,100,000
Treasury stock, shares issued, beginning at Dec. 31, 2024	33,499,638					33,500,000
Beginning balance at Dec. 31, 2024	$ 2,438.9	$ 42.7	847.1	3,208.1	(209.6)	$ 1,449.4
Stock Issued During Period, Shares, New Issues		200,000
Stock Issued During Period, Value, New Issues		$ 0.1
Stock Repurchased During Period, Shares						(100,000)
APIC, Share-based Payment Arrangement, Increase for Cost Recognition			23.8
Net income	$ 236.3
Dividends declared (in dollars per share)	$ 1.83
Dividends, Common Stock, Cash				(67.7)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ (106.1)				(106.1)
Common stock, shares issued, ending at Sep. 30, 2025	69,304,151	69,300,000
Treasury stock, shares issued, ending at Sep. 30, 2025	33,625,347					33,600,000
Ending balance at Sep. 30, 2025	$ 2,718.9	$ 42.8	870.9	3,376.7	(103.5)	$ 1,468.0
Stock repurchases	(18.6)					$ (18.6)
Common stock, shares issued, beginning at Jun. 30, 2025		69,300,000
Treasury stock, shares issued, beginning at Jun. 30, 2025						33,600,000
Beginning balance at Jun. 30, 2025		$ 42.8	864.2	3,317.0	(87.8)	$ 1,466.5
Stock Issued During Period, Shares, New Issues		0
Stock Issued During Period, Value, New Issues		$ 0.0
Stock Repurchased During Period, Shares						0
APIC, Share-based Payment Arrangement, Increase for Cost Recognition			6.7
Net income	$ 82.2
Dividends declared (in dollars per share)	$ 0.61
Dividends, Common Stock, Cash				(22.5)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ 15.7				15.7
Common stock, shares issued, ending at Sep. 30, 2025	69,304,151	69,300,000
Treasury stock, shares issued, ending at Sep. 30, 2025	33,625,347					33,600,000
Ending balance at Sep. 30, 2025	$ 2,718.9	$ 42.8	$ 870.9	$ 3,376.7	$ (103.5)	$ 1,468.0
Stock repurchases						$ (1.5)