Schedule of Quarterly Data (Detail) - USD ($) $ / shares in Units, $ 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
Income Statement [Abstract]
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
Net income attributable to American Vanguard	$ 7,416	$ 6,525	$ 5,599	$ 4,655	$ 8,429	$ 4,089	$ 4,304	$ 3,452	$ 24,195	$ 20,274	$ 12,788
Basic net income per share	$ 0.25	$ 0.22	$ 0.19	$ 0.16	$ 0.29	$ 0.14	$ 0.15	$ 0.12	$ 0.83	$ 0.70	$ 0.44
Diluted net income per share	$ 0.25	$ 0.22	$ 0.19	$ 0.16	$ 0.28	$ 0.14	$ 0.15	$ 0.12	$ 0.81	$ 0.68	$ 0.44