Consolidated Statements of Shareholders’ Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]
Beginning balance at Dec. 31, 2015	$ 1,992.4	$ 5.1	$ 654.0	$ 1,209.0	$ 124.3
Beginning Balance, shares at Dec. 31, 2015		51.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	16.8			16.8
Other Comprehensive Income (Note 12)	12.7				12.7
Cash Dividends to Shareholders	(49.2)			(49.2)
Repurchases of Common Stock	$ (3.8)	$ 0.0	(1.8)	(2.0)
Repurchases of Common Stock, shares	(0.1)	(0.1)
Equity-based Compensation Cost	$ 4.7		4.7
Equity-based Awards, Net of Shares Exchanged	1.6		3.4	(1.8)
Equity-based Awards, Net of Shares Exchanged, shares		0.1
Ending Balance, shares at Dec. 31, 2016		51.3
Ending balance at Dec. 31, 2016	1,975.2	$ 5.1	660.3	1,172.8	137.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	120.9			120.9
Other Comprehensive Income (Note 12)	57.4				57.4
Cash Dividends to Shareholders	(49.5)			(49.5)
Equity-based Compensation Cost	9.4		9.4
Equity-based Awards, Net of Shares Exchanged	1.7		3.4	(1.7)
Equity-based Awards, Net of Shares Exchanged, shares		0.2
Ending Balance, shares at Dec. 31, 2017		51.5
Ending balance at Dec. 31, 2017	2,115.6	$ 5.1	673.1	1,243.0	194.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	190.1			190.1
Other Comprehensive Income (Note 12)	(190.8)				(190.8)
Cash Dividends to Shareholders	(56.4)			(56.4)
Stock Issued During Period, Shares, New Issues		(13.1)
Stock Issued During Period, Value, New Issues	(978.6)	$ (1.4)	(977.2)	0.0
Equity-based Compensation Cost	18.6		18.6
Equity-based Awards, Net of Shares Exchanged	(5.6)		(2.6)	(3.0)
Equity-based Awards, Net of Shares Exchanged, shares		0.1
Ending Balance, shares at Dec. 31, 2018		64.7
Ending balance at Dec. 31, 2018	$ 3,050.1	$ 6.5	$ 1,666.3	$ 1,355.5	$ 21.8