Summary of Business Sales by Product and Geographic Location (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net sales
Net sales	$ 131,338	$ 111,780	$ 107,046	$ 104,108	$ 116,494	$ 89,975	$ 77,905	$ 70,673	$ 454,272	$ 355,047	$ 312,113
Gross profit	$ 52,983	$ 45,300	$ 43,297	$ 41,051	$ 44,941	$ 38,032	$ 34,335	$ 30,084	182,631	147,392	128,288
Crop
Net sales
Gross profit									150,986	117,892	107,821
Non-crop
Net sales
Gross profit									31,645	29,500	20,467
Insecticides
Net sales
Net sales									150,595	134,377	119,226
Herbicides/Soil Fumigants/Fungicides
Net sales
Net sales									183,350	124,529	123,540
Other, Including Plant Growth Regulators
Net sales
Net sales									58,360	42,503	29,438
Crop
Net sales
Net sales									392,305	301,409	272,204
Non-Crop
Net sales
Net sales									$ 61,967	$ 53,638	$ 39,909