Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	AOCI Attributable to Parent
Balance at Dec. 31, 2019	$ 364.9	$ 0.6	$ 555.7	$ 1,008.2	$ (823.5)	$ (376.1)
Balance at Dec. 31, 2019		47,992,348
Balance at Dec. 31, 2019					14,271,047
Stock issuance, net, shares		246,001
Cash dividends - per common share	(19.5)			(19.5)
Share-based employee compensation	(4.0)		(4.0)
Net earnings (loss)	(175.9)			(175.9)
Other comprehensive income (Loss)	271.8					271.8
Acquisition of treasury stock	(34.4)				$ (34.4)
Acquisition of treasury stock, shares		(382,170)			382,170
Balance at Jun. 30, 2020	402.9	$ 0.6	551.7	812.8	$ (857.9)	(104.3)
Balance at Jun. 30, 2020		47,856,179
Balance at Jun. 30, 2020					14,653,217
Balance at Mar. 31, 2020	370.4	$ 0.6	557.3	772.1	$ (857.9)	(101.7)
Balance at Mar. 31, 2020		47,659,955
Balance at Mar. 31, 2020					14,653,217
Stock issuance, net, shares		196,224
Cash dividends - per common share	(9.6)			(9.6)
Share-based employee compensation	(5.6)		(5.6)
Net earnings (loss)	50.3			50.3
Other comprehensive income (Loss)	(2.6)					(2.6)
Balance at Jun. 30, 2020	402.9	$ 0.6	551.7	812.8	$ (857.9)	(104.3)
Balance at Jun. 30, 2020		47,856,179
Balance at Jun. 30, 2020					14,653,217
Balance at Dec. 31, 2020	$ 450.9	$ 0.6	553.7	869.8	$ (863.9)	(109.3)
Balance at Dec. 31, 2020	47,913,821	47,913,821
Balance at Dec. 31, 2020					14,685,510
Stock issuance, net, shares		139,215
Cash dividends - per common share	$ (20.5)			(20.5)
Share-based employee compensation	1.0		1.0
Net earnings (loss)	90.5			90.5
Other comprehensive income (Loss)	6.4					6.4
Acquisition of treasury stock	(30.0)				$ (30.0)
Acquisition of treasury stock, shares		(320,093)			320,093
Balance at Jun. 30, 2021	$ 498.3	$ 0.6	554.7	939.8	$ (893.9)	(102.9)
Balance at Jun. 30, 2021	47,732,943	47,732,943
Balance at Jun. 30, 2021					15,005,603
Balance at Mar. 31, 2021	$ 473.6	$ 0.6	556.6	895.0	$ (873.9)	(104.7)
Balance at Mar. 31, 2021		47,828,464
Balance at Mar. 31, 2021					14,811,145
Stock issuance, net, shares		98,937
Cash dividends - per common share	(10.3)			(10.3)
Share-based employee compensation	(1.9)		(1.9)
Net earnings (loss)	55.1			55.1
Other comprehensive income (Loss)	1.8					1.8
Acquisition of treasury stock	(20.0)				$ (20.0)
Acquisition of treasury stock, shares		(194,458)			194,458
Balance at Jun. 30, 2021	$ 498.3	$ 0.6	$ 554.7	$ 939.8	$ (893.9)	$ (102.9)
Balance at Jun. 30, 2021	47,732,943	47,732,943
Balance at Jun. 30, 2021					15,005,603