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, shares at Dec. 31, 2020		47,913,821			14,685,510
Stock issuance, net			0.1		$ (0.1)
Stock issuance, net, shares		173,379			2,445
Cash dividends - per common share	(41.6)			(41.6)
Share-based employee compensation	7.5		7.5
Net earnings	183.2			183.2
Other comprehensive income (loss)	(0.3)					(0.3)
Acquisition of treasury stock	(80.0)				$ (80.0)
Acquisition of treasury stock, shares		(784,901)			784,901
Ending Balance at Dec. 31, 2021	519.7	$ 0.6	561.3	1,011.4	$ (944.0)	(109.6)
Balance, shares at Dec. 31, 2021		47,302,299			15,472,856
Stock issuance, net, shares		159,628			2,037
Cash dividends - per common share	(44.4)			(44.4)
Share-based employee compensation	12.3		12.3
Net earnings	202.9			202.9
Other comprehensive income (loss)	9.5					9.5
Acquisition of treasury stock	(165.0)				$ (165.0)
Acquisition of treasury stock, shares		(1,889,742)			1,889,742
Ending Balance at Dec. 31, 2022	$ 535.0	$ 0.6	573.6	1,169.9	$ (1,109.0)	(100.1)
Balance, shares at Dec. 31, 2022	45,572,185	45,572,185			17,364,635
Stock issuance, net			0.1		$ (0.1)
Stock issuance, net, shares		115,701			1,819
Cash dividends - per common share	$ (47.1)			(47.1)
Share-based employee compensation	18.0		18.0
Net earnings	223.8			223.8
Other comprehensive income (loss)	(4.6)					(4.6)
Acquisition of treasury stock	(133.3)				$ (133.3)
Acquisition of treasury stock, shares		(1,785,825)			1,785,825
Ending Balance at Dec. 31, 2023	$ 591.8	$ 0.6	$ 591.7	$ 1,346.6	$ (1,242.4)	$ (104.7)
Balance, shares at Dec. 31, 2023	43,902,061	43,902,061			19,152,279