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, 2016	$ 3,532	$ 33	$ 194,177	$ (64,985)	$ 253	$ 133,010	$ 4,380	$ 137,390
Balance (in shares) at Dec. 31, 2016	883	33,032
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock options exercised		$ 1	2,476			2,477		2,477
Common stock options exercised (in shares)		762
Sale of subsidiary shares to noncontrolling interests			1,765			1,765	235	2,000
Stock-based compensation			1,405			1,405		1,405
Issuance of common stock in the form of restricted stock (in shares)		312
Issuance of common stock, net of stock issuance costs		$ 5	31,856			31,861		31,861
Issuance of common stock, net of stock issuance costs (in shares)		5,307
Net income (loss)				10,148		10,148	(87)	10,061
Net dividend declared by joint ventures							(465)	(465)
Other comprehensive income					3,154	3,154	434	3,588
Balance, end 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
Stock-based compensation			1,925			1,925		1,925
Purchase of subsidiary shares from noncontrolling interest			187			187	(1,794)	(1,607)
Restricted stock awards canceled		(10)
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					(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)
Stock-based compensation			2,346			2,346		2,346
Purchase of subsidiary shares from noncontrolling interest			(74)			(74)	(339)	(413)
Restricted stock awards canceled		(20)
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)	(1,766)
Other comprehensive income								(2,383)
Balance, end of period at Dec. 31, 2019	$ 3,532	$ 41	$ 236,956	$ (47,783)	$ (4,862)	$ 187,885	$ 4,877	$ 192,762
Balance (in shares) at Dec. 31, 2019	883	40,632