Condensed Consolidated Statements of Shareholders’ Equity - USD ($) $ in Millions	Total	Common Stock	Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Previously Reported	Previously Reported Common Stock	Previously Reported Paid-in Capital	Previously Reported Retained Earnings	Previously Reported Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2018							64,700,000
Beginning balance at Dec. 31, 2018						$ 3,050.1	$ 6.5	$ 1,666.3	$ 1,355.5	$ 21.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	$ 531.1			$ 531.1
Other Comprehensive Income (Loss), Net of Taxes (Note 13)	314.3				$ 314.3
Cash Dividends and Dividend Equivalents to Shareholders	$ (68.4)			(68.4)
Dividends paid to shareholders per share (in dollars per share)	$ 1.03
Equity-based Compensation Cost (Note 17)	$ 25.3		$ (1.3)
Equity-based Awards, Net of Shares Exchanged (Note 11) (in shares)		400,000
Equity-based Awards, Net of Shares Exchanged (Note 17)	(9.2)	$ 0.0	25.3	(7.9)
Issuances of Common Stock (in shares)		1,600,000
Issuances of Common Stock	127.2	$ 0.2	127.0	0.0
Shares Issued Under Employee Stock Purchase Plan (Note 14)	1.9		1.9
Ending balance (in shares) at Dec. 31, 2019							66,700,000
Ending balance at Dec. 31, 2019						$ 3,972.3	$ 6.7	$ 1,819.2	$ 1,810.3	$ 336.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	409.9			409.9
Other Comprehensive Income (Loss), Net of Taxes (Note 13)	344.4				344.4
Cash Dividends and Dividend Equivalents to Shareholders	$ (79.4)			(79.4)
Dividends paid to shareholders per share (in dollars per share)	$ 1.20
Repurchases of Common Stock (in shares)	1,617,000
Equity-based Compensation Cost (Note 17)	$ 24.9		0.9
Equity-based Awards, Net of Shares Exchanged (Note 11) (in shares)		300,000
Equity-based Awards, Net of Shares Exchanged (Note 17)	(2.7)	$ 0.0	24.9	(3.6)
Issuances of Common Stock	(110.4)	$ (0.2)	(44.2)	(66.0)
Stock Repurchased During Period, Shares		(1,600,000)
Shares Issued Under Employee Stock Purchase Plan (Note 14)	4.4		4.4
Ending balance (in shares) at Dec. 31, 2020		65,400,000
Ending balance at Dec. 31, 2020	4,563.4	$ 6.5	1,805.2	2,071.2	680.5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)	(120.5)			(120.5)
Other Comprehensive Income (Loss), Net of Taxes (Note 13)	(232.4)				(232.4)
Cash Dividends and Dividend Equivalents to Shareholders	$ (81.0)			(81.0)
Dividends paid to shareholders per share (in dollars per share)	$ 1.24
Repurchases of Common Stock (in shares)	2,085,000
Equity-based Compensation Cost (Note 17)	$ 37.0		37.0
Equity-based Awards, Net of Shares Exchanged (Note 11) (in shares)		300,000
Equity-based Awards, Net of Shares Exchanged (Note 17)	(2.5)	$ 0.1	0.9	(3.5)
Issuances of Common Stock (in shares)		100,000
Stock Repurchased During Period, Shares		(2,100,000)
Shares Issued Under Employee Stock Purchase Plan (Note 14)	5.4		5.4
Ending balance (in shares) at Dec. 31, 2021		63,700,000
Ending balance at Dec. 31, 2021	4,007.7	$ 6.4	1,790.7	1,762.5	$ 448.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Repurchased During Period, Value	$ (161.7)	$ (0.2)	$ (57.8)	$ (103.7)