Revenue and Segment Information - Revenue, Income, Goodwill and Identifiable Assets by Location (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net Sales	$ 257,125	$ 213,276	$ 495,212	$ 428,665
Income from Operations	26,786	20,307	48,147	40,558
Goodwill	83,972		83,972		$ 84,761
Total Identifiable Assets	725,379		725,379		639,671
Industrial
Segment Reporting Information [Line Items]
Net Sales	150,031	117,342	282,198	243,158
Income from Operations	16,165	11,052	27,965	23,622
Goodwill	61,405		61,405		61,682
Total Identifiable Assets	408,735		408,735		369,271
Agricultural
Segment Reporting Information [Line Items]
Net Sales	59,071	54,221	117,718	105,998
Income from Operations	6,186	5,858	11,439	10,717
Goodwill	6,267		6,267		6,357
Total Identifiable Assets	169,744		169,744		141,023
European
Segment Reporting Information [Line Items]
Net Sales	48,023	41,713	95,296	79,509
Income from Operations	4,435	$ 3,397	8,743	$ 6,219
Goodwill	16,300		16,300		16,722
Total Identifiable Assets	$ 146,900		$ 146,900		$ 129,377