Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	AOCI Attributable to Parent
Beginning 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
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	90.5			90.5
Other comprehensive income	6.4					6.4
Acquisition of treasury stock	(30.0)				$ (30.0)
Acquisition of treasury stock, shares		(320,093)			320,093
Ending 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
Balance at Jun. 30, 2021					15,005,603
Beginning 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	55.1			55.1
Other comprehensive income	1.8					1.8
Acquisition of treasury stock	(20.0)				$ (20.0)
Acquisition of treasury stock, shares		(194,458)			194,458
Ending 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
Balance at Jun. 30, 2021					15,005,603
Beginning Balance at Dec. 31, 2021	$ 519.7	$ 0.6	561.3	1,011.4	$ (944.0)	(109.6)
Balance at Dec. 31, 2021	47,302,299	47,302,299
Balance at Dec. 31, 2021					15,472,856
Stock issuance, net, shares		100,677
Cash dividends - per common share	$ (22.0)			(22.0)
Share-based employee compensation	4.4		4.4
Net earnings	96.6			96.6
Other comprehensive income	14.1					14.1
Acquisition of treasury stock	(85.0)				$ (85.0)
Acquisition of treasury stock, shares		(940,155)			940,155
Ending Balance at Jun. 30, 2022	$ 527.8	$ 0.6	565.7	1,086.0	$ (1,029.0)	(95.5)
Balance at Jun. 30, 2022	46,462,821	46,462,821
Balance at Jun. 30, 2022					16,413,011
Beginning Balance at Mar. 31, 2022	$ 537.6	$ 0.6	563.9	1,044.8	$ (974.0)	(97.7)
Balance at Mar. 31, 2022		47,018,645
Balance at Mar. 31, 2022					15,773,861
Stock issuance, net, shares		83,326
Cash dividends - per common share	(11.0)			(11.0)
Share-based employee compensation	1.8		1.8
Net earnings	52.2			52.2
Other comprehensive income	2.2					2.2
Acquisition of treasury stock	(55.0)				$ (55.0)
Acquisition of treasury stock, shares		(639,150)			639,150
Ending Balance at Jun. 30, 2022	$ 527.8	$ 0.6	$ 565.7	$ 1,086.0	$ (1,029.0)	$ (95.5)
Balance at Jun. 30, 2022	46,462,821	46,462,821
Balance at Jun. 30, 2022					16,413,011