Consolidated Statements of Shareholders’ Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income
Beginning balance (in shares) at Dec. 31, 2020		65.4
Beginning 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)	123.2			123.2
Other Comprehensive Income (Loss), Net of Tax	$ (290.0)				(290.0)
Dividends paid to shareholders per share (in dollars per share)	$ 0.31
Cash Dividends and Dividend Equivalents to Shareholders	$ (21.0)			(21.0)
Repurchases of Common Stock (in shares)		0.6
Repurchases of Common Stock (Note 10)	(47.1)	$ 0.0	(16.4)	(30.7)
Shares Issued Under Employee Stock Purchase Plan (Note 10)			1.2
Shares Issued Under Employee Stock Purchase Plan (Note 10)	1.2
Equity-based Compensation Cost	12.3		12.3
Equity-based Awards, Net of Shares Exchanged (in shares)		0.2
Equity-based Awards, Net of Shares Exchanged	(2.9)	$ 0.0	(0.2)	(2.7)
Ending balance (in shares) at Mar. 31, 2021		65.0
Ending balance at Mar. 31, 2021	4,339.1	$ 6.5	1,802.1	2,140.0	390.5
Beginning balance (in shares) at Dec. 31, 2021		63.7
Beginning 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]
Net Income (Loss)	(94.8)			(94.8)
Other Comprehensive Income (Loss), Net of Tax	$ (510.4)				(510.4)
Dividends paid to shareholders per share (in dollars per share)	$ 0.31
Cash Dividends and Dividend Equivalents to Shareholders	$ (19.6)			(19.6)
Repurchases of Common Stock (in shares)		0.0
Repurchases of Common Stock (Note 10)	0.0	$ 0.0	0.0	0.0
Shares Issued Under Employee Stock Purchase Plan (Note 10)	1.3	$ 0.0	1.3
Equity-based Compensation Cost	11.9		11.9
Equity-based Awards, Net of Shares Exchanged (in shares)		0.1
Equity-based Awards, Net of Shares Exchanged	(1.6)	$ 0.0	(0.8)	(0.8)
Ending balance (in shares) at Mar. 31, 2022		63.8
Ending balance at Mar. 31, 2022	$ 3,394.5	$ 6.4	$ 1,803.1	$ 1,647.3	$ (62.3)