Schedule of Selected Unaudited Statement of Operations Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Net sales	$ 130,521	$ 124,884	$ 113,104	$ 99,676	$ 131,338	$ 111,780	$ 107,046	$ 104,108	$ 468,186	$ 454,272	$ 355,047
Gross profit	46,536	47,463	41,653	41,702	52,983	45,300	43,297	41,051	177,354	182,631	147,392
Net income attributable to American Vanguard	$ 3,436	$ 3,153	$ 3,106	$ 3,906	$ 7,416	$ 6,525	$ 5,599	$ 4,655	$ 13,601	$ 24,195	$ 20,274
Basic net income per share	$ 0.12	$ 0.11	$ 0.11	$ 0.13	$ 0.25	$ 0.22	$ 0.19	$ 0.16	$ 0.47	$ 0.83	$ 0.70
Diluted net income per share	$ 0.12	$ 0.11	$ 0.11	$ 0.13	$ 0.25	$ 0.22	$ 0.19	$ 0.16	$ 0.46	$ 0.81	$ 0.68