Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net sales:
Net sales:	$ 912,380	$ 844,748	$ 879,577
Cost of sales	677,687	639,649	677,129
Gross profit	234,693	205,099	202,448
Selling, general and administrative expenses	145,955	137,479	135,920
Income from operations	88,738	67,620	66,528
Interest expense	(4,839)	(5,914)	(6,724)
Interest income	336	214	189
Other income	(1,868)	269	6,874
Income before income taxes	82,367	62,189	66,867
Provision for income taxes	38,052	22,144	23,658
Net income	$ 44,315	$ 40,045	$ 43,209
Net income per common share:
Basic (in dollars per share)	$ 3.84	$ 3.50	$ 3.81
Diluted (in dollars per share)	$ 3.79	$ 3.46	$ 3.76
Average common shares:
Basic (in shares)	11,549	11,434	11,349
Diluted (in shares)	11,682	11,565	11,482
Industrial
Net sales:
Net sales:	$ 522,706	$ 484,088	$ 498,761
Income from operations	51,914	35,984	42,194
Agricultural
Net sales:
Net sales:	227,389	205,834	208,257
Income from operations	24,059	20,720	17,295
European
Net sales:
Net sales:	162,285	154,826	172,559
Income from operations	$ 12,765	$ 10,916	$ 7,039