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		140,823
Cash dividends - per common share	(30.5)			(30.5)
Share-based employee compensation	4.0		4.0
Net earnings	141.3			141.3
Other comprehensive income	6.5					6.5
Acquisition of treasury stock	(50.0)				$ (50.0)
Acquisition of treasury stock, shares		(507,022)			507,022
Ending Balance at Sep. 30, 2021	522.2	$ 0.6	557.7	980.6	$ (913.9)	(102.8)
Balance at Sep. 30, 2021		47,547,622
Balance at Sep. 30, 2021					15,192,532
Beginning 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
Stock issuance, net, shares		1,608
Cash dividends - per common share	(10.0)			(10.0)
Share-based employee compensation	3.0		3.0
Net earnings	50.8			50.8
Other comprehensive income	0.1					0.1
Acquisition of treasury stock	(20.0)				$ (20.0)
Acquisition of treasury stock, shares		(186,929)			186,929
Ending Balance at Sep. 30, 2021	522.2	$ 0.6	557.7	980.6	$ (913.9)	(102.8)
Balance at Sep. 30, 2021		47,547,622
Balance at Sep. 30, 2021					15,192,532
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		106,490
Cash dividends - per common share	$ (32.7)			(32.7)
Share-based employee compensation	8.0		8.0
Net earnings	154.1			154.1
Other comprehensive income	17.1					17.1
Acquisition of treasury stock	(145.0)				$ (145.0)
Acquisition of treasury stock, shares		(1,636,950)			1,636,950
Ending Balance at Sep. 30, 2022	$ 521.2	$ 0.6	569.3	1,132.8	$ (1,089.0)	(92.5)
Balance at Sep. 30, 2022	45,771,839	45,771,839
Balance at Sep. 30, 2022					17,109,806
Beginning 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
Balance at Jun. 30, 2022					16,413,011
Stock issuance, net, shares		5,813
Cash dividends - per common share	(10.7)			(10.7)
Share-based employee compensation	3.6		3.6
Net earnings	57.5			57.5
Other comprehensive income	3.0					3.0
Acquisition of treasury stock	(60.0)				$ (60.0)
Acquisition of treasury stock, shares		(696,795)			696,795
Ending Balance at Sep. 30, 2022	$ 521.2	$ 0.6	$ 569.3	$ 1,132.8	$ (1,089.0)	$ (92.5)
Balance at Sep. 30, 2022	45,771,839	45,771,839
Balance at Sep. 30, 2022					17,109,806