Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Net sales	$ 302,794	$ 314,707
Cost of goods sold	257,021	273,381
Gross profit	45,773	41,326
Selling, general, and administrative expenses	22,290	24,999
Operating income	23,483	16,327
Net interest and other income	884	1,079
Income before income taxes	24,367	17,406
Provision for income taxes	5,760	3,995
Net income	$ 18,607	$ 13,411
Earnings per common and common equivalent share - basic (in usd per share)	$ 0.89	$ 0.64
Earnings per common and common equivalent share - diluted (in usd per share)	$ 0.89	$ 0.64
Weighted average common and common equivalent shares outstanding - basic (in shares)	20,792	20,884
Weighted average common and common equivalent shares outstanding - diluted (in shares)	20,851	20,983
Cash dividends declared per share (in usd per share)	$ 0.02	$ 0.02