Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Par	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Balance at Dec. 31, 2019	$ 1,446.1	$ 1.1	$ 829.9	$ 1,978.9	$ (118.7)	$ (1,245.1)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	42.4			42.4
Dividends paid on common stock	(14.2)			(14.2)
Change in other comprehensive income (loss)– net of tax	(36.6)				(36.6)
Stock based compensation	8.0		15.2			(7.2)
Acquisition of treasury stock	(24.6)					(24.6)
Balance at Mar. 31, 2020	1,421.1	1.1	845.1	2,007.1	(155.3)	(1,276.9)
Balance at Dec. 31, 2019	1,446.1	1.1	829.9	1,978.9	(118.7)	(1,245.1)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	51.1
Change in other comprehensive income (loss)– net of tax	33.5
Balance at Sep. 30, 2020	1,499.4	1.1	845.1	2,015.8	(85.2)	(1,277.4)
Balance at Mar. 31, 2020	1,421.1	1.1	845.1	2,007.1	(155.3)	(1,276.9)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(1.0)			(1.0)
Change in other comprehensive income (loss)– net of tax	17.3				17.3
Stock based compensation	(0.5)		(0.5)
Balance at Jun. 30, 2020	1,436.9	1.1	844.6	2,006.1	(138.0)	(1,276.9)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	9.7			9.7
Change in other comprehensive income (loss)– net of tax	52.8				52.8
Stock based compensation			0.5			(0.5)
Balance at Sep. 30, 2020	1,499.4	1.1	845.1	2,015.8	(85.2)	(1,277.4)
Balance at Dec. 31, 2020	1,510.2	1.1	849.7	1,996.4	(59.6)	(1,277.4)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(14.0)			(14.0)
Change in other comprehensive income (loss)– net of tax	(19.1)				(19.1)
Stock based compensation	9.8		11.8			(2.0)
Balance at Mar. 31, 2021	1,486.9	1.1	861.5	1,982.4	(78.7)	(1,279.4)
Balance at Dec. 31, 2020	1,510.2	1.1	849.7	1,996.4	(59.6)	(1,277.4)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(2.8)
Change in other comprehensive income (loss)– net of tax	(34.2)				(34.2)
Balance at Sep. 30, 2021	1,494.3	1.1	873.4	1,993.6	(93.8)	(1,280.0)
Balance at Mar. 31, 2021	1,486.9	1.1	861.5	1,982.4	(78.7)	(1,279.4)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	2.2			2.2
Change in other comprehensive income (loss)– net of tax	5.5				5.5
Stock based compensation	8.2		8.2
Balance at Jun. 30, 2021	1,502.8	1.1	869.7	1,984.6	(73.2)	(1,279.4)
Increase (Decrease) in Stockholders' Equity
Net income (loss)	9.0			9.0
Change in other comprehensive income (loss)– net of tax	(20.6)				(20.6)
Stock based compensation	3.1		3.7			(0.6)
Balance at Sep. 30, 2021	$ 1,494.3	$ 1.1	$ 873.4	$ 1,993.6	$ (93.8)	$ (1,280.0)