Unaudited Quarterly Consolidated Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unaudited Quarterly Consolidated Financial Data
Revenue	$ 26,332	$ 28,168	$ 23,557	$ 20,616	$ 20,269	$ 21,872	$ 20,495	$ 18,713	$ 98,673	$ 81,349	$ 77,502
Gross Profit	9,798	11,133	7,256	6,288	7,523	7,578	6,027	5,253	34,475	26,381	16,829
Net income (loss) attributable to AXT, Inc	$ 3,134	$ 4,419	$ 1,930	$ 665	$ 2,214	$ 2,229	$ 1,151	$ 42	$ 10,148	$ 5,636	$ (2,228)
Net (loss) attributable to AXT, Inc per share, basic (in dollar per share)	$ 0.08	$ 0.11	$ 0.05	$ 0.02	$ 0.07	$ 0.07	$ 0.03	$ 0.00	$ 0.27	$ 0.17	$ (0.07)
Net (loss) attributable to AXT, Inc per share, diluted (in dollar per share)	$ 0.08	$ 0.11	$ 0.05	$ 0.02	$ 0.06	$ 0.07	$ 0.03	$ 0.00	$ 0.26	$ 0.17	$ (0.07)