Investments in Privately Held Companies - Minority Investment Entities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Summarized income information of all the minority investment entities that are not consolidated and accounted for under the equity method [Abstract]
Net income (loss)	$ (1,200,000)	$ (43,000)	$ 569,000
AXT, Inc. Stockholders' Equity
Summarized income information of all the minority investment entities that are not consolidated and accounted for under the equity method [Abstract]
Net Revenue	6,441,000	9,112,000	11,887,000
Gross (loss) profit	(542,000)	1,954,000	5,340,000
Operating (loss) income	(1,828,000)	494,000	2,059,000
Net income (loss)	(1,995,000)	462,000	1,528,000
Minority Investment Entities [Member]
Summarized income information of all the minority investment entities that are not consolidated and accounted for under the equity method [Abstract]
Net Revenue	24,851,000	36,259,000	47,824,000
Gross (loss) profit	(2,344,000)	8,327,000	21,436,000
Operating (loss) income	(7,388,000)	2,494,000	9,046,000
Net income (loss)	(7,947,000)	2,371,000	6,765,000
Summarized balance sheet information of all the minority investment entities that are not consolidated and accounted for under the equity method [Abstract]
Current assets	32,210,000	32,097,000
Noncurrent assets	31,770,000	35,917,000
Current liabilities	24,449,000	18,185,000
Noncurrent liabilities	406,000	571,000
Minority investment entities
Dividends received	0	305,000	$ 327,000
Undistributed retained earnings	$ 4,700,000	$ 6,600,000