Accounting for Stock-Based Compensation (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Stock-based compensation in the form of employee stock options and restricted stock awards, included in [Abstract]
Total stock-based compensation	$ 300,000	$ 216,000	$ 873,000	$ 638,000
Tax effect on stock-based compensation	0	0	0	0
Net effect on net income	300,000	216,000	873,000	638,000
Effect on net income attributable to AXT, Inc. per common share [Abstract]
Basic (in dollars per share)	$ (0.01)	$ (0.01)	$ (0.03)	$ (0.02)
Diluted (in dollars per share)	$ (0.01)	$ (0.01)	$ (0.03)	$ (0.02)
Compensation costs related to unvested stock options not yet recognized	1,600,000		1,600,000
Value of estimated forfeitures			91,000
Weighted-average period of amortization			2 years 3 months 17 days
Stock options granted during the period (in shares)	0	0	104,000	0
Weighted average grant date fair value (in dollars per share)			$ 2.84	$ 0
Weighted-average assumptions [Abstract]
Expected term			4 years
Volatility (in hundredths)			73.74%
Expected dividend (in hundredths)			0.00%
Risk-free interest rate (in hundredths)			0.71%
Shares [Abstract]
Options outstanding, beginning of period (in shares)			2,380,000
Granted (in shares)	0	0	104,000	0
Exercised (in shares)	(26,000)	(51,579)	(126,000)	(250,591)
Canceled and expired (in shares)			(30,000)
Options outstanding, end of period (in shares)	2,328,000		2,328,000		2,380,000
Options vested and expected to vest, end of period (in shares)	2,292,000		2,292,000
Options exercisable, end of period (in shares)	1,501,000		1,501,000
Weighted-average Exercise Price [Roll Forward]
Options outstanding, beginning of period (in dollars per share)			$ 3.25
Granted (in dollars per share)			$ 5.22
Exercised (in dollars per share)			$ 2.19
Canceled and expired (in dollars per share)			$ 9.69
Options outstanding, end of period (in dollars per share)	$ 3.31		$ 3.31		$ 3.25
Options vested and expected to vest, end of period (in dollars per share)	$ 3.29		$ 3.29
Options exercisable, end of period (in dollars per share)	$ 2.69		$ 2.69
Weighted-average Remaining Contractual Life [Abstract]
Options outstanding, beginning of period			6 years 0 months 17 days		6 years 3 months
Options outstanding, end of period			6 years 0 months 17 days		6 years 3 months
Options vested and expected to vest, end of period			6 years
Options exercisable, end of period			4 years 9 months
Aggregate Intrinsic Value [Abstract]
Options outstanding, beginning of period			3,456,000
Options outstanding, end of period	2,151,000		2,151,000		3,456,000
Options vested and expected to vest, end of period	2,146,000		2,146,000
Options exercisable, end of period	1,882,000		1,882,000
Closing price (in dollars per share)	$ 3.38		$ 3.38
In-the-money options exercisable (in shares)	1,152,553		1,152,553
Options Outstanding
Options outstanding, shares (in shares)	2,327,695		2,327,695
Weighted-average Exercise Price (in dollars per share)	$ 3.31		$ 3.31
Weighted-average Remaining Contractual Life			6 years 0 months 17 days
Options Exercisable
Options exercisable, shares (in shares)	1,501,285		1,501,285
Weighted-average Exercise Price (in dollars per share)	$ 2.69		$ 2.69
Options exercised during the period (in shares)	26,000	51,579	126,000	250,591
Intrinsic value of options exercised	18,000	334,000	383,000	1,500,000
Proceeds from common stock options exercised			276,000	637,000
Shares [Roll Forward]
Non-vested, beginning of period (in shares)			223,127
Granted (in shares)			30,768	16,548
Vested (in shares)			(77,812)	(72,300)
Non-vested, end of period (in shares)	176,083		176,083		223,127
Weighted-Average Grant Date Fair Value [Roll Forward]
Non-vested, beginning of period (in dollars per share)			$ 4.47
Granted (in dollars per share)			$ 3.90	$ 7.25
Vested (in dollars per share)			$ 3.09	$ 2.77
Non-vested, end of period (in dollars per share)	$ 4.98		$ 4.98		$ 4.47
Unrecognized compensation expense related to restricted stock awards	721,000		721,000
Weighted average period for recognizing costs			2 years 3 months 17 days
$1.18 - $1.38 [Member]
Options Outstanding
Range of exercise price, minimum (in dollars per share)			$ 1.18
Range of exercise price, maximum (in dollars per share)			$ 1.38
Options outstanding, shares (in shares)	407,001		407,001
Weighted-average Exercise Price (in dollars per share)	$ 1.31		$ 1.31
Weighted-average Remaining Contractual Life			1 year 8 months 22 days
Options Exercisable
Options exercisable, shares (in shares)	407,001		407,001
Weighted-average Exercise Price (in dollars per share)	$ 1.31		$ 1.31
$1.40 - $1.40 [Member]
Options Outstanding
Range of exercise price, minimum (in dollars per share)			$ 1.40
Range of exercise price, maximum (in dollars per share)			$ 1.40
Options outstanding, shares (in shares)	1,094		1,094
Weighted-average Exercise Price (in dollars per share)	$ 1.40		$ 1.40
Weighted-average Remaining Contractual Life			2 years 5 months 12 days
Options Exercisable
Options exercisable, shares (in shares)	1,094		1,094
Weighted-average Exercise Price (in dollars per share)	$ 1.40		$ 1.40
$1.59 - $1.59 [Member]
Options Outstanding
Range of exercise price, minimum (in dollars per share)			$ 1.59
Range of exercise price, maximum (in dollars per share)			$ 1.59
Options outstanding, shares (in shares)	328,460		328,460
Weighted-average Exercise Price (in dollars per share)	$ 1.59		$ 1.59
Weighted-average Remaining Contractual Life			6 years 6 months 14 days
Options Exercisable
Options exercisable, shares (in shares)	273,967		273,967
Weighted-average Exercise Price (in dollars per share)	$ 1.59		$ 1.59
$1.88 - $1.91 [Member]
Options Outstanding
Range of exercise price, minimum (in dollars per share)			$ 1.88
Range of exercise price, maximum (in dollars per share)			$ 1.91
Options outstanding, shares (in shares)	8,000		8,000
Weighted-average Exercise Price (in dollars per share)	$ 1.90		$ 1.90
Weighted-average Remaining Contractual Life			2 years
Options Exercisable
Options exercisable, shares (in shares)	8,000		8,000
Weighted-average Exercise Price (in dollars per share)	$ 1.90		$ 1.90
$2.04 - $2.04 [Member]
Options Outstanding
Range of exercise price, minimum (in dollars per share)			$ 2.04
Range of exercise price, maximum (in dollars per share)			$ 2.04
Options outstanding, shares (in shares)	441,775		441,775
Weighted-average Exercise Price (in dollars per share)	$ 2.04		$ 2.04
Weighted-average Remaining Contractual Life			7 years 0 months 25 days
Options Exercisable
Options exercisable, shares (in shares)	313,481		313,481
Weighted-average Exercise Price (in dollars per share)	$ 2.04		$ 2.04
$2.19 - $4.09 [Member]
Options Outstanding
Range of exercise price, minimum (in dollars per share)			$ 2.19
Range of exercise price, maximum (in dollars per share)			$ 4.09
Options outstanding, shares (in shares)	175,510		175,510
Weighted-average Exercise Price (in dollars per share)	$ 2.80		$ 2.80
Weighted-average Remaining Contractual Life			2 years
Options Exercisable
Options exercisable, shares (in shares)	151,510		151,510
Weighted-average Exercise Price (in dollars per share)	$ 2.62		$ 2.62
$4.79 - $4.79 [Member]
Options Outstanding
Range of exercise price, minimum (in dollars per share)			$ 4.79
Range of exercise price, maximum (in dollars per share)			$ 4.79
Options outstanding, shares (in shares)	366,500		366,500
Weighted-average Exercise Price (in dollars per share)	$ 4.79		$ 4.79
Weighted-average Remaining Contractual Life			9 years 0 months 28 days
Options Exercisable
Options exercisable, shares (in shares)	0		0
Weighted-average Exercise Price (in dollars per share)	$ 0.00		$ 0.00
$4.81 - $5.61 [Member]
Options Outstanding
Range of exercise price, minimum (in dollars per share)			$ 4.81
Range of exercise price, maximum (in dollars per share)			$ 5.61
Options outstanding, shares (in shares)	144,610		144,610
Weighted-average Exercise Price (in dollars per share)	$ 5.26		$ 5.26
Weighted-average Remaining Contractual Life			7 years 1 month 5 days
Options Exercisable
Options exercisable, shares (in shares)	64,610		64,610
Weighted-average Exercise Price (in dollars per share)	$ 4.84		$ 4.84
$5.83 - $5.83 [Member]
Options Outstanding
Range of exercise price, minimum (in dollars per share)			$ 5.83
Range of exercise price, maximum (in dollars per share)			$ 5.83
Options outstanding, shares (in shares)	362,450		362,450
Weighted-average Exercise Price (in dollars per share)	$ 5.83		$ 5.83
Weighted-average Remaining Contractual Life			7 years 10 months 2 days
Options Exercisable
Options exercisable, shares (in shares)	200,431		200,431
Weighted-average Exercise Price (in dollars per share)	$ 5.83		$ 5.83
$6.31 - $7.82 [Member]
Options Outstanding
Range of exercise price, minimum (in dollars per share)			$ 6.31
Range of exercise price, maximum (in dollars per share)			$ 7.82
Options outstanding, shares (in shares)	92,295		92,295
Weighted-average Exercise Price (in dollars per share)	$ 6.65		$ 6.65
Weighted-average Remaining Contractual Life			5 years 8 months 22 days
Options Exercisable
Options exercisable, shares (in shares)	81,191		81,191
Weighted-average Exercise Price (in dollars per share)	$ 6.48		$ 6.48
Cost of revenue [Member]
Stock-based compensation in the form of employee stock options and restricted stock awards, included in [Abstract]
Total stock-based compensation	19,000	20,000	56,000	60,000
Selling, general and administrative [Member]
Stock-based compensation in the form of employee stock options and restricted stock awards, included in [Abstract]
Total stock-based compensation	245,000	184,000	721,000	543,000
Research and development [Member]
Stock-based compensation in the form of employee stock options and restricted stock awards, included in [Abstract]
Total stock-based compensation	$ 36,000	$ 12,000	$ 96,000	$ 35,000