Unaudited Quarterly Consolidated Financial Data (Details) - 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
Unaudited Quarterly Consolidated Financial Data
Revenue	$ 18,410	$ 19,841	$ 24,797	$ 20,208	$ 22,232	$ 28,626	$ 27,120	$ 24,419	$ 83,256	$ 102,397	$ 98,673
Gross profit	3,865	5,759	8,506	6,695	5,850	10,614	11,010	9,573	24,825	37,047	34,475
Net income (loss) attributable to AXT, Inc.	$ (2,049)	$ (898)	$ 1,451	$ (1,104)	$ (1,061)	$ 3,939	$ 3,901	$ 2,875	$ (2,600)	$ 9,654	$ 10,148
Net income (loss) attributable to AXT, Inc. per share, basic (in dollar per share)	$ (0.05)	$ (0.02)	$ 0.04	$ (0.03)	$ (0.03)	$ 0.10	$ 0.10	$ 0.07	$ (0.07)	$ 0.24	$ 0.27
Net income (loss) attributable to AXT, Inc. per share, diluted (in dollar per share)	$ (0.05)	$ (0.02)	$ 0.04	$ (0.03)	$ (0.03)	$ 0.10	$ 0.10	$ 0.07	$ (0.07)	$ 0.24	$ 0.26