Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Numerator:
Net income attributable to AXT, Inc.	$ 5,546	$ 4,385	$ 8,711	$ 7,810
Less: Preferred stock dividends	(44)	(44)	(88)	(88)
Net income available to common stockholders	$ 5,502	$ 4,341	$ 8,623	$ 7,722
Weighted-average number of common shares outstanding:
Denominator for basic net income (loss) per share - weighted-average common shares	42,001,000	41,248,000	41,935,000	41,124,000
Effect of dilutive securities:
Denominator for dilutive net income per common shares	42,511,000	42,727,000	42,586,000	42,725,000
Net income attributable to AXT, Inc. per common share:
Basic	$ 0.13	$ 0.11	$ 0.21	$ 0.19
Diluted	$ 0.13	$ 0.10	$ 0.20	$ 0.18
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)	392,000	21,000	220,000	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)	362,000	99,000	352,000	90,000
Options
Effect of dilutive securities:
Effect of dilutive securities (in shares)	284,000	889,000	379,000	986,000
Restricted stock awards
Effect of dilutive securities:
Effect of dilutive securities (in shares)	226,000	590,000	272,000	615,000