Stockholders' Equity and Stock Repurchase Program (Details) (USD $)	0 Months Ended	3 Months Ended		12 Months Ended
	Oct. 27, 2014	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2013	Dec. 31, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period		$ 144,688,000
Common stock options exercised		76,000
Common stock repurchased		(617,000)
Stock-based compensation		274,000
Net (loss) income		(899,000)	(1,835,000)
Dividends declared by joint ventures		(83,000)
Change in unrealized (loss) gain on marketable securities		(259,000)	(10,000)
Currency translation adjustment		238,000
Balance, end of period		143,418,000
Stock Repurchase Program [Abstract]
Stock repurchase program, authorized amount	5,000,000	6,000,000
Shares repurchased (in shares)		230,000		285,000
Average price of shares repurchased (in dollars per share)		$ 2.67		$ 2.51
Total purchase price		617,000		716,000
Stock repurchase program remaining authorized repurchase amount		4,400,000		5,300,000
Preferred Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period					3,532,000
Balance, end of period		3,532,000			3,532,000
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period					32,000
Balance, end of period		32,000			32,000
Additional Paid In Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period		195,419,000
Common stock options exercised		76,000
Common stock repurchased		(617,000)
Stock-based compensation		274,000
Balance, end of period		195,152,000
Accumulated Deficit [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period		(68,393,000)
Net (loss) income		(1,024,000)
Balance, end of period		(69,417,000)
Other Comprehensive Income/(Loss) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period		7,673,000
Change in unrealized (loss) gain on marketable securities		(259,000)
Currency translation adjustment		206,000
Balance, end of period		7,620,000
AXT, Inc. Stockholders' Equity [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period		138,263,000
Common stock options exercised		76,000
Common stock repurchased		(617,000)
Stock-based compensation		274,000
Net (loss) income		(1,000)
Change in unrealized (loss) gain on marketable securities		(259,000)
Currency translation adjustment		206,000
Balance, end of period		136,919,000
Noncontrolling Interests [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period		6,425,000
Net (loss) income		125,000
Dividends declared by joint ventures		(83,000)
Currency translation adjustment		32,000
Balance, end of period		$ 6,499,000