Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Numerator:
Net income attributable to AXT, Inc.	$ 5,759	$ 3,800	$ 14,470	$ 11,610
Less: Preferred stock dividends	(44)	(44)	(132)	(132)
Net income available to common stockholders	$ 5,715	$ 3,756	$ 14,338	$ 11,478
Denominator:
Denominator for basic net income (loss) per share - weighted-average common shares	42,163,000	41,460,000	42,011,000	41,237,000
Effect of dilutive securities:
Denominator for dilutive net income per common shares	42,982,000	42,678,000	42,718,000	42,710,000
Net income attributable to AXT, Inc. per common share:
Basic	$ 0.14	$ 0.09	$ 0.34	$ 0.28
Diluted	$ 0.13	$ 0.09	$ 0.34	$ 0.27
Preferred stock, shares issued (in shares)	883,000		883,000		883,000
Preferred stock, shares outstanding (in shares)	883,000		883,000		883,000
Preferred stock, par value (in dollars per share)	$ 0.001		$ 0.001		$ 0.001
Preferred stock, value	$ 3,532		$ 3,532		$ 3,532
Cumulative annual dividend rate (as a percent)			5.00%		5.00%
Liquidation preference over common stock (in dollars per share)	$ 4		$ 4		$ 4
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from diluted net income (loss) per share as the impact is anti-dilutive (in shares)	184,000	124,000	201,000	21,000
Restricted stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from diluted net income (loss) per share as the impact is anti-dilutive (in shares)	69,000	138,000	202,000	112,000
Options
Effect of dilutive securities:
Effect of dilutive securities (in shares)	440,000	691,000	399,000	887,000
Restricted stock awards
Effect of dilutive securities:
Effect of dilutive securities (in shares)	379,000	527,000	308,000	586,000

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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