Investments in Companies (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) employee item	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) employee item	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Summary of investments [Abstract]
Income allocated to minority interests	$ 5,000	$ 226,000	$ 257,000	$ 673,000
Equity investments classified as other assets	14,721,000		$ 14,721,000		$ 14,975,000
Investments in unconsolidated privately-held entities, included in other assets					200,000
Employee duration			27 years
AXT, Inc. Stockholders' Equity [Member]
Summary of investments [Abstract]
Gross equity earnings from minority-owned joint ventures that are not consolidated, recorded as other income	805,000	1,759,000	$ 3,546,000	6,485,000
Equity Method Investments [Member]
Summary of investments [Abstract]
Equity method investment by parent	$ 8,245,000		$ 8,245,000		8,095,000
Number of equity investment entities | item	3		3
Equity investments classified as other assets	$ 8,200,000		$ 8,200,000		8,100,000
Gross equity earnings from minority-owned joint ventures that are not consolidated, recorded as other income	$ 167,000	390,000	$ 777,000	1,500,000
Joint Ventures [Member]
Summary of investments [Abstract]
Number of consolidated joint ventures | item	3		3
Income from three consolidated joint ventures	$ 500,000	1,100,000	$ 1,700,000	2,900,000
Income allocated to minority interests	5,000	226,000	257,000	673,000
Net income from joint ventures attributable to parent	454,000	$ 837,000	1,400,000	$ 2,200,000
Minority investment in consolidated joint venture, included in other assets	4,300,000		4,300,000		4,000,000
Majority-Owned Subsidiaries [Member]
Summary of investments [Abstract]
Investments, consolidated	$ 5,269,000		$ 5,269,000		5,269,000
Beijing JiYa Semiconductor Material Co., Ltd [Member]
Summary of investments [Abstract]
Number of persons on board | employee	5		5
Beijing JiYa Semiconductor Material Co., Ltd [Member] | Majority-Owned Subsidiaries [Member]
Summary of investments [Abstract]
Investments, consolidated	$ 3,331,000		$ 3,331,000		3,331,000
Percentage of ownership, consolidated method (in hundredths)			46.00%
Nanjing Jin Mei Gallium Co., Ltd [Member]
Summary of investments [Abstract]
Number of new board representatives | employee			2
Nanjing Jin Mei Gallium Co., Ltd [Member] | Majority-Owned Subsidiaries [Member]
Summary of investments [Abstract]
Investments, consolidated	592,000		$ 592,000		592,000
Percentage of ownership, consolidated method (in hundredths)			83.00%
Beijing BoYu Semiconductor Vessel Craftwork Technology Co., Ltd [Member]
Summary of investments [Abstract]
Number of new board representatives | employee			2
Beijing BoYu Semiconductor Vessel Craftwork Technology Co., Ltd [Member] | Majority-Owned Subsidiaries [Member]
Summary of investments [Abstract]
Investments, consolidated	1,346,000		$ 1,346,000		1,346,000
Percentage of ownership, consolidated method (in hundredths)			70.00%
Donghai County Dongfang High Purity Electronic Materials Co., Ltd [Member] | Equity Method Investments [Member]
Summary of investments [Abstract]
Equity method investment by parent	$ 1,557,000		$ 1,557,000		1,723,000
Percentage of ownership, equity method (in hundredths)	46.00%		46.00%
Xilingol Tongli Germanium Co. Ltd [Member] | Equity Method Investments [Member]
Summary of investments [Abstract]
Equity method investment by parent	$ 5,606,000		$ 5,606,000		5,351,000
Percentage of ownership, equity method (in hundredths)	25.00%		25.00%
Emeishan Jia Mei High Purity Metals Co., Ltd [Member] | Equity Method Investments [Member]
Summary of investments [Abstract]
Equity method investment by parent	$ 1,082,000		$ 1,082,000		$ 1,021,000
Percentage of ownership, equity method (in hundredths)	25.00%		25.00%