Revenue and Segment Information - Revenue, Income, Goodwill and Identifiable Assets by Location (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Segment Reporting Information [Line Items]
Net Sales	$ 257,572	$ 240,455	$ 752,784	$ 669,120
Income from Operations	28,249	27,761	76,396	68,319
Goodwill	83,716		83,716		$ 84,761
Total Identifiable Assets	734,773		734,773		639,671
Industrial
Segment Reporting Information [Line Items]
Net Sales	156,721	132,388	438,919	375,546
Income from Operations	18,351	14,941	46,316	38,563
Goodwill	61,546		61,546		61,682
Total Identifiable Assets	419,444		419,444		369,271
Agricultural
Segment Reporting Information [Line Items]
Net Sales	61,464	64,923	179,182	170,921
Income from Operations	6,608	8,598	18,047	19,315
Goodwill	6,009		6,009		6,357
Total Identifiable Assets	167,851		167,851		141,023
European
Segment Reporting Information [Line Items]
Net Sales	39,387	43,144	134,683	122,653
Income from Operations	3,290	$ 4,222	12,033	$ 10,441
Goodwill	16,161		16,161		16,722
Total Identifiable Assets	$ 147,478		$ 147,478		$ 129,377