Industry Segment and Geographic Data, Operating Income to Earnings (Details) - USD ($) $ 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
Reconciliation of segment operating income to net earnings [Abstract]
Operating Income										$ 108,895	$ 94,495	$ 81,268
Other non-operating income (expense), net										812	2,587	(411)
Interest expense										2,328	5,286	4,026
Earnings from continuing operations before taxes										107,379	91,796	76,831
Income tax expense										26,962	22,745	19,977
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
Discontinued operations, net of tax		(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
Long-lived assets [Abstract]
Long-lived assets	[1]	313,234				326,025				313,234	326,025	254,574
United States [Member]
Long-lived assets [Abstract]
Long-lived assets	[1]	241,053				253,384				241,053	253,384	198,494
Canada [Member]
Long-lived assets [Abstract]
Long-lived assets	[1]	4,470				4,659				4,470	4,659	2,718
Mexico [Member]
Long-lived assets [Abstract]
Long-lived assets	[1]	10,586				12,036				10,586	12,036	4,012
Asia [Member]
Long-lived assets [Abstract]
Long-lived assets	[1]	40,621				38,942				40,621	38,942	32,470
Europe [Member]
Long-lived assets [Abstract]
Long-lived assets	[1]	$ 16,504				$ 17,004				$ 16,504	$ 17,004	$ 16,880

[1] Long-lived assets are attributed to countries based upon the location of the assets.