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, 2017	$ 384.1	$ 0.6	$ 516.8	$ 598.2	$ (385.6)	$ (345.9)
Balance at Dec. 31, 2017		52,772,139
Balance at Dec. 31, 2017					8,010,597
Cumulative effect impact of ASU adoption | ASU 2018-02 [Member]	(54.3)			54.3		(54.3)
Stock issuance, net		651,726
Share-based employee compensation	18.9		18.9
Net earnings	75.1			75.1
Other comprehensive (loss)	(4.2)					(4.2)
Acquisition of treasury stock	(105.0)				$ (105.0)
Acquisition of treasury stock, shares		(1,785,816)			1,785,816
Balance at Jun. 30, 2018	368.9	$ 0.6	535.7	727.6	$ (490.6)	(404.4)
Balance at Jun. 30, 2018		51,638,049
Balance at Jun. 30, 2018					9,796,413
Balance at Mar. 31, 2018	368.6	$ 0.6	532.0	680.3	$ (455.6)	(388.7)
Balance at Mar. 31, 2018		52,198,476
Balance at Mar. 31, 2018					9,175,844
Stock issuance, net		60,142
Share-based employee compensation	3.7		3.7
Net earnings	47.3			47.3
Other comprehensive (loss)	(15.7)					(15.7)
Acquisition of treasury stock	(35.0)				$ (35.0)
Acquisition of treasury stock, shares		(620,569)			620,569
Balance at Jun. 30, 2018	368.9	$ 0.6	535.7	727.6	$ (490.6)	(404.4)
Balance at Jun. 30, 2018		51,638,049
Balance at Jun. 30, 2018					9,796,413
Balance at Dec. 31, 2018	$ 226.0	$ 0.6	547.4	829.8	$ (692.2)	(459.6)
Balance at Dec. 31, 2018	48,808,239	48,808,239
Balance at Dec. 31, 2018	12,745,485				12,745,485
Cumulative effect impact of ASU adoption | ASU 2017-12 [Member]	$ 0.1			(0.1)		0.1
Stock issuance, net		501,398
Cash dividends - $0.175 per common share	(17.6)			(17.6)
Share-based employee compensation	(9.3)		(9.3)
Net earnings	93.6			93.6
Other comprehensive (loss)	(1.5)					(1.5)
Acquisition of treasury stock	(48.1)				$ (48.1)
Acquisition of treasury stock, shares		(647,691)			647,691
Balance at Jun. 30, 2019	$ 243.1	$ 0.6	538.1	905.7	$ (740.3)	(461.0)
Balance at Jun. 30, 2019	48,661,946	48,661,946
Balance at Jun. 30, 2019	13,393,176				13,393,176
Balance at Mar. 31, 2019	$ 245.1	$ 0.6	553.3	859.9	$ (712.2)	(456.5)
Balance at Mar. 31, 2019		48,640,635
Balance at Mar. 31, 2019					13,077,171
Stock issuance, net		337,316
Cash dividends - $0.175 per common share	(8.7)			(8.7)
Share-based employee compensation	(15.2)		(15.2)
Net earnings	54.5			54.5
Other comprehensive (loss)	(4.5)					(4.5)
Acquisition of treasury stock	(28.1)				$ (28.1)
Acquisition of treasury stock, shares		(316,005)			316,005
Balance at Jun. 30, 2019	$ 243.1	$ 0.6	$ 538.1	$ 905.7	$ (740.3)	$ (461.0)
Balance at Jun. 30, 2019	48,661,946	48,661,946
Balance at Jun. 30, 2019	13,393,176				13,393,176