CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	AXT, Inc. Stockholders' Equity	Noncontrolling Interests	Total
Balance, beginning of period at Dec. 31, 2017	$ 3,532	$ 39	$ 231,679	$ (54,837)	$ 3,407	$ 183,820	$ 4,497	$ 188,317
Balance (in shares) at Dec. 31, 2017	883	39,413
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock options exercised		$ 1	627			628		628
Common stock options exercised (in shares)		238
Purchase of subsidiary shares from noncontrolling interest			187			187	(1,794)	(1,607)
Restricted stock awards canceled		(10)
Stock-based compensation			1,925			1,925		1,925
Issuance of common stock in the form of restricted stock (in shares)		344
Net income (loss)				9,654		9,654	1,355	11,009
Other comprehensive income (loss)					(5,379)	(5,379)	(361)	(5,740)
Balance, end of period at Dec. 31, 2018	$ 3,532	$ 40	234,417	(45,183)	(1,972)	190,835	3,697	194,532
Balance (in shares) at Dec. 31, 2018	883	39,985
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock options exercised		$ 1	267			268		268
Common stock options exercised (in shares)		113
Reclassification out of accumulated other comprehensive income and non-controlling interest upon the deconsolidation of a subsidiary					(1,150)	(1,150)	533	(617)
Purchase of subsidiary shares from noncontrolling interest			(74)			(74)	(339)	(413)
Restricted stock awards canceled		(20)
Stock-based compensation			2,346			2,346		2,346
Issuance of common stock in the form of restricted stock (in shares)		554
Net income (loss)				(2,600)		(2,600)	1,012	(1,588)
Other comprehensive income (loss)					(1,740)	(1,740)	(26)	(2,383)
Other comprehensive income (loss)								(1,766)
Balance, end of period at Dec. 31, 2019	$ 3,532	$ 41	236,957	(47,783)	(4,862)	187,885	4,877	192,762
Balance (in shares) at Dec. 31, 2019	883	40,632
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock options exercised		$ 1	2,535			2,536		2,536
Common stock options exercised (in shares)		905
Sale of subsidiary shares to noncontrolling interests			396			396		396
Purchase of subsidiary shares from noncontrolling interest			(1,398)			(1,398)	(202)	(1,600)
Restricted stock awards canceled		(13)
Stock-based compensation			2,623			2,623		2,623
Issuance of common stock in the form of restricted stock (in shares)		443
Net income (loss)				3,238		3,238	1,803	5,041
Adjustment to noncontrolling interests in connection with the reorganization and alignment of assets under Tongmei			(10,732)			(10,732)	10,732	(10,732)
Net dividend declared by joint ventures							(2,238)	(2,238)
Other comprehensive income (loss)					8,071	8,071	378	8,449
Balance, end of period at Dec. 31, 2020	$ 3,532	$ 42	$ 230,381	$ (44,545)	$ 3,209	$ 192,619	$ 15,350	$ 207,969
Balance (in shares) at Dec. 31, 2020	883	41,967