Stockholders' Equity (Details) - USD ($)	3 Months Ended						9 Months Ended		12 Months Ended	96 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2015	Dec. 31, 2023	Oct. 27, 2014
Stockholders' Equity
Balance, beginning of period	$ 223,352,000	$ 224,510,000	$ 227,483,000	$ 232,991,000	$ 243,418,000	$ 244,900,000	$ 227,483,000	$ 244,900,000
Common stock options exercised	3,000	5,000	20,000		2,000	8,000
Investment in subsidiary with noncontrolling interest				199,000	306,000	203,000
Investment in subsidiary with redeemable noncontrolling interest				(44,000)	(75,000)	(36,000)
Noncontrolling interest portion of Tongmei stock-based compensation	(7,000)	(8,000)	(11,000)	(71,000)	17,000	17,000
Stock-based compensation	723,000	621,000	614,000	703,000	720,000	717,000
Tongmei stock-based compensation	97,000	94,000	195,000	188,000	192,000	198,000
Net loss	(2,747,000)	(1,200,000)	(1,977,000)	(6,059,000)	(5,051,000)	(3,517,000)
Other comprehensive income (loss)	3,561,000	(670,000)	(1,814,000)	(460,000)	(6,538,000)	928,000
Balance, end of period	224,982,000	223,352,000	224,510,000	227,447,000	232,991,000	243,418,000	224,982,000	227,447,000		$ 227,483,000
Net income (loss) attributable to redeemable noncontrolling interests	(140,000)			(356,000)			(210,000)	(807,000)
Other comprehensive loss attributable to redeemable noncontrolling interests	376,000			(55,000)			118,000	(615,000)
Reclassification adjustment from AOCI	$ 0			0			$ 0	0
Stock repurchase program, authorized amount											$ 5,000,000.0
Shares repurchased (in shares)	0						0		908,000	0
Average price of shares repurchased (in dollars per share)									$ 2.52
Total purchase price									$ 2,300,000
Stock repurchase program remaining authorized repurchase amount	$ 2,700,000						$ 2,700,000
Preferred Stock
Stockholders' Equity
Balance, beginning of period	3,532,000	3,532,000	3,532,000	3,532,000	3,532,000	3,532,000	3,532,000	3,532,000
Balance, end of period	3,532,000	3,532,000	3,532,000	3,532,000	3,532,000	3,532,000	3,532,000	3,532,000		$ 3,532,000
Common Stock
Stockholders' Equity
Balance, beginning of period	44,000	44,000	44,000	44,000	44,000	44,000	44,000	44,000
Common stock options exercised	1,000
Balance, end of period	45,000	44,000	44,000	44,000	44,000	44,000	45,000	44,000		44,000
Additional Paid-In Capital
Stockholders' Equity
Balance, beginning of period	239,962,000	239,257,000	238,452,000	236,988,000	236,192,000	235,308,000	238,452,000	235,308,000
Common stock options exercised	2,000	5,000	20,000		2,000	8,000
Investment in subsidiary with noncontrolling interest				(43,000)	(74,000)	(36,000)
Investment in subsidiary with redeemable noncontrolling interest				(44,000)	(75,000)	(36,000)
Noncontrolling interest portion of Tongmei stock-based compensation	(14,000)	(15,000)	(24,000)	(139,000)	31,000	33,000
Stock-based compensation	723,000	621,000	614,000	703,000	720,000	717,000
Tongmei stock-based compensation	97,000	94,000	195,000	188,000	192,000	198,000
Balance, end of period	240,770,000	239,962,000	239,257,000	237,653,000	236,988,000	236,192,000	240,770,000	237,653,000		238,452,000
Accumulated Deficit
Stockholders' Equity
Balance, beginning of period	(35,639,000)	(34,123,000)	(32,040,000)	(22,596,000)	(17,507,000)	(14,159,000)	(32,040,000)	(14,159,000)
Net loss	(2,937,000)	(1,516,000)	(2,083,000)	(5,823,000)	(5,089,000)	(3,348,000)
Balance, end of period	(38,576,000)	(35,639,000)	(34,123,000)	(28,419,000)	(22,596,000)	(17,507,000)	(38,576,000)	(28,419,000)		(32,040,000)
Accumulated Other Comprehensive Income (Loss)
Stockholders' Equity
Balance, beginning of period	(8,227,000)	(7,626,000)	(5,999,000)	(8,175,000)	(2,260,000)	(3,118,000)	(5,999,000)	(3,118,000)
Other comprehensive income (loss)	3,189,000	(601,000)	(1,627,000)	(406,000)	(5,915,000)	858,000
Balance, end of period	(5,038,000)	(8,227,000)	(7,626,000)	(8,581,000)	(8,175,000)	(2,260,000)	(5,038,000)	(8,581,000)		(5,999,000)
AXT, Inc. Stockholders' Equity
Stockholders' Equity
Balance, beginning of period	199,672,000	201,084,000	203,989,000	209,793,000	220,001,000	221,607,000	203,989,000	221,607,000
Common stock options exercised	3,000	5,000	20,000		2,000	8,000
Investment in subsidiary with noncontrolling interest				(43,000)	(74,000)	(36,000)
Investment in subsidiary with redeemable noncontrolling interest				(44,000)	(75,000)	(36,000)
Noncontrolling interest portion of Tongmei stock-based compensation	(14,000)	(15,000)	(24,000)	(139,000)	31,000	33,000
Stock-based compensation	723,000	621,000	614,000	703,000	720,000	717,000
Tongmei stock-based compensation	97,000	94,000	195,000	188,000	192,000	198,000
Net loss	(2,937,000)	(1,516,000)	(2,083,000)	(5,823,000)	(5,089,000)	(3,348,000)
Other comprehensive income (loss)	3,189,000	(601,000)	(1,627,000)	(406,000)	(5,915,000)	858,000
Balance, end of period	200,733,000	199,672,000	201,084,000	204,229,000	209,793,000	220,001,000	200,733,000	204,229,000		203,989,000
Noncontrolling Interests
Stockholders' Equity
Balance, beginning of period	23,680,000	23,426,000	23,494,000	23,198,000	23,417,000	23,293,000	23,494,000	23,293,000
Investment in subsidiary with noncontrolling interest				242,000	380,000	239,000
Noncontrolling interest portion of Tongmei stock-based compensation	7,000	7,000	13,000	68,000	(14,000)	(16,000)
Net loss	190,000	316,000	106,000	(236,000)	38,000	(169,000)
Other comprehensive income (loss)	372,000	(69,000)	(187,000)	(54,000)	(623,000)	70,000
Balance, end of period	$ 24,249,000	$ 23,680,000	$ 23,426,000	$ 23,218,000	$ 23,198,000	$ 23,417,000	$ 24,249,000	$ 23,218,000		$ 23,494,000