Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Par	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock, Common [Member]
Beginning Balance at Dec. 31, 2021	$ 1,485.5	$ 1.1	$ 878.6	$ 2,012.5	$ (126.5)	$ (1,280.2)
Increase (Decrease) in Stockholders' Equity
Net income	17.8			17.8
Dividends paid on common stock	(8.5)			(8.5)
Change in other comprehensive (loss)- net of tax	(17.6)				(17.6)
Stock based compensation	9.9		11.3			(1.4)
Ending Balance at Mar. 31, 2022	1,487.1	1.1	889.9	2,021.8	(144.1)	(1,281.6)
Beginning Balance at Dec. 31, 2021	1,485.5	1.1	878.6	2,012.5	(126.5)	(1,280.2)
Increase (Decrease) in Stockholders' Equity
Net income	89.3
Change in other comprehensive (loss)- net of tax	(122.6)
Ending Balance at Sep. 30, 2022	1,445.0	1.1	898.9	2,076.4	(249.1)	(1,282.3)
Beginning Balance at Mar. 31, 2022	1,487.1	1.1	889.9	2,021.8	(144.1)	(1,281.6)
Increase (Decrease) in Stockholders' Equity
Net income	44.7			44.7
Dividends paid on common stock	(8.5)			(8.5)
Change in other comprehensive (loss)- net of tax	(47.2)				(47.2)
Stock based compensation	4.2		4.2
Ending Balance at Jun. 30, 2022	1,480.3	1.1	894.1	2,058.0	(191.3)	(1,281.6)
Increase (Decrease) in Stockholders' Equity
Net income	26.8			26.8
Dividends paid on common stock	(8.4)			(8.4)
Change in other comprehensive (loss)- net of tax	(57.8)				(57.8)
Stock based compensation	4.1					(0.7)
Ending Balance at Sep. 30, 2022	1,445.0	1.1	898.9	2,076.4	(249.1)	(1,282.3)
Beginning Balance at Dec. 31, 2022	1,554.2	1.1	905.0	2,104.9	(174.4)	(1,282.4)
Increase (Decrease) in Stockholders' Equity
Net income	42.7			42.7
Dividends paid on common stock	(10.4)			(10.4)
Change in other comprehensive (loss)- net of tax	22.3				22.3
Stock based compensation	13.4		15.8			(2.4)
Ending Balance at Mar. 31, 2023	1,622.2	1.1	920.8	2,137.2	(152.1)	(1,284.8)
Beginning Balance at Dec. 31, 2022	1,554.2	1.1	905.0	2,104.9	(174.4)	(1,282.4)
Increase (Decrease) in Stockholders' Equity
Net income	123.9
Change in other comprehensive (loss)- net of tax	6.7				6.7
Ending Balance at Sep. 30, 2023	1,646.3	1.1	931.5	2,197.3	(167.7)	(1,315.9)
Beginning Balance at Mar. 31, 2023	1,622.2	1.1	920.8	2,137.2	(152.1)	(1,284.8)
Increase (Decrease) in Stockholders' Equity
Net income	42.5			42.5
Dividends paid on common stock	(10.5)			(10.5)
Change in other comprehensive (loss)- net of tax	6.9				6.9
Stock based compensation	5.0		5.1			(0.1)
Ending Balance at Jun. 30, 2023	1,666.1	1.1	925.9	2,169.2	(145.2)	(1,284.9)
Increase (Decrease) in Stockholders' Equity
Net income	38.7			38.7
Dividends paid on common stock	(10.6)			10.6
Repurchases of common stock	(30.1)					(30.1)
Change in other comprehensive (loss)- net of tax	(22.5)				(22.5)
Stock based compensation	4.7		5.6			(0.9)
Ending Balance at Sep. 30, 2023	$ 1,646.3	$ 1.1	$ 931.5	$ 2,197.3	$ (167.7)	$ (1,315.9)