Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Selected quarterly financial information [Abstract]
Net sales	$ 282,738	$ 343,609	$ 247,939	$ 254,302	$ 241,252	$ 307,723	$ 305,172	$ 283,766	$ 1,128,588	[1]	$ 1,137,913	[1]	$ 1,092,051	[1]
Gross profit	94,154	107,748	64,358	70,395	72,844	92,088	88,905	77,963	336,655		331,800		312,787
Earnings from continuing operations	22,742	36,212	11,842	9,621	12,738	22,654	20,555	13,104	80,417		69,051		56,854
Loss from discontinued operations, net of taxes	(13,568)	(7,587)	(875)	(994)	(1,220)	(7,903)	(1,123)	(888)	(23,024)		(11,134)		(13,851)
Net earnings	$ 9,174	$ 28,625	$ 10,967	$ 8,627	$ 11,518	$ 14,751	$ 19,432	$ 12,216	$ 57,393		$ 57,917		$ 43,003
Net earnings from continuing operations per common share [Abstract]
Basic (in dollars per share)	$ 1.02	$ 1.62	$ 0.53	$ 0.43	$ 0.57	$ 1.01	$ 0.92	$ 0.58	$ 3.59		$ 3.09		$ 2.53
Diluted (in dollars per share)	1.00	1.59	0.52	0.42	0.56	1.00	0.90	0.57	3.52		3.03		2.48
Net earnings per common share [Abstract]
Basic (in dollars per share)	0.41	1.28	0.49	0.38	0.51	0.66	0.87	0.54	2.57		2.59		1.91
Diluted (in dollars per share)	$ 0.40	$ 1.26	$ 0.48	$ 0.38	$ 0.50	$ 0.65	$ 0.85	$ 0.53	$ 2.51		$ 2.54		$ 1.88

[1] Segment net sales include intersegment sales in our Engine Management and Temperature Control segments.