Stock-Based Compensation (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Mar. 28, 2013
Stock-based compensation in the form of employee stock options and restricted stock [Abstract]
Total stock-based compensation	$ 332,000	281,000
Tax effect on stock-based compensation	0	0
Net effect on net income (loss)	332,000	281,000
Effect on net income (loss) attributable to AXT, Inc. per common share [Abstract]
Basic	$ (0.01)	(0.01)
Diluted	$ (0.01)	(0.01)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value of stock options granted (in dollars per share)	$ 0	3.05
Weighted average assumptions [Abstract]
Expected term (in years)	4 years
Volatility (in hundredths)	73.41%
Expected dividend (in hundredths)	0.00%
Risk-free interest rate (in hundredths)	0.76%
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation costs related to unvested stock options not yet recognized	1,900,000
Value of estimated forfeitures	31,000
Weighted-average period of amortization	2 years 7 months 6 days
Number of options outstanding [Roll Forward]
Options outstanding, beginning of period (in shares)	2,727,000
Granted (in shares)	0	80,000
Exercised (in shares)	(183,000)
Canceled and expired (in shares)	(26,000)
Options outstanding, end of period (in shares)	2,518,000		2,727,000
Options vested and expected to vest as of March 31, 2013 (in shares)	2,502,000
Options exercisable as of March 31, 2013 (in shares)	1,523,000
Weighted average exercise price [Roll Forward]
Options outstanding, beginning of period (in dollars per share)	$ 3.28
Granted (in dollars per share)	$ 0
Exercised (in dollars per share)	$ 1.40
Canceled and expired (in dollars per share)	$ 3.80
Options outstanding, end of period (in dollars per share)	$ 3.41		$ 3.28
Options vested and expected to vest as of March 31, 2013 (in dollars per share)	$ 3.41
Options exercisable as of March 31, 2013 (in dollars per share)	$ 3.14
Weighted average Remaining Contractual Life [Abstract]
Options outstanding, beginning of period	6 years 10 months 2 days		6 years 8 months 16 days
Options outstanding, end of period	6 years 10 months 2 days		6 years 8 months 16 days
Options vested and expected to vest, end of period	6 years 9 months 29 days
Option exercisable, end of period	5 years 6 months 29 days
Aggregate Intrinsic Value [Abstract]
Options outstanding, beginning of period	1,353,000
Options outstanding, end of period	1,239,000		1,353,000
Options vested and expected to vest, aggregate intrinsic value	1,238,000
Options exercisable, end of period	1,137,000
Closing price (in dollars per share)				$ 2.94
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average period of amortization	2 years 2 months 12 days
Shares [Roll Forward]
Non-vested, beginning of period (in shares)	238,723
Granted (in shares)	0
Vested (in shares)	0
Non-vested, end of period (in shares)	238,723
Weighted Average Grant Date Fair Value [Roll Forward]
Non-vested, beginning of period (in dollars per share)	$ 4.27
Granted (in dollars per share)	$ 0
Vested (in dollars per share)	$ 0
Non-vested, end of period (in dollars per share)	$ 4.27
Unrecognized compensation expense related to restricted stock awards	768,000
Cost of revenue [Member]
Stock-based compensation in the form of employee stock options and restricted stock [Abstract]
Total stock-based compensation	6,000	18,000
Selling, general and administrative [Member]
Stock-based compensation in the form of employee stock options and restricted stock [Abstract]
Total stock-based compensation	284,000	238,000
Research and development [Member]
Stock-based compensation in the form of employee stock options and restricted stock [Abstract]
Total stock-based compensation	$ 42,000	25,000