Net Income Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Numerator:
Net income attributable to AXT, Inc.	$ 932	$ 6,484	$ 3,866	$ 17,754
Less: Preferred stock dividends	(44)	(44)	(132)	(132)
Net income available to common stockholders	888	6,440	3,734	17,622
Denominator:
Denominator for basic net income per share - weighted average common shares (in shares)	32,183	31,944	32,118	31,832
Effect of Dilutive Securities on Earnings Per Share [Line Items]
Denominator for dilutive net income per common share (in shares)	32,769	33,126	32,911	33,140
Net income attributable to AXT, Inc. per common share:
Basic (in dollars per share)	$ 0.03	$ 0.20	$ 0.12	$ 0.55
Diluted (in dollars per share)	$ 0.03	$ 0.19	$ 0.11	$ 0.53
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)	883		883		883
Preferred stock, shares outstanding (in shares)	883		883		883
Preferred stock, par value (in dollars per share)	$ 0.001		$ 0.001		$ 0.001
Preferred stock, value	$ 3,532		$ 3,532		$ 3,532	[1]
Cumulative annual dividend rate (in hundredths)	5.00%		5.00%		5.00%
Liquidation preference over common stock (in dollars per share)	$ 4		$ 4		$ 4
Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from diluted net income per share as the impact is anti-dilutive (in shares)	992	407	977	403
Restricted stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from diluted net income per share as the impact is anti-dilutive (in shares)	172	163	14	163
Restricted stock [Member]
Effect of Dilutive Securities on Earnings Per Share [Line Items]
Effect of dilutive securities (in shares)	4	88	39	116
Common stock options [Member]
Effect of Dilutive Securities on Earnings Per Share [Line Items]
Effect of dilutive securities (in shares)	582	1,094	754	1,192

[1] The Condensed Consolidated Balance Sheet at December 31, 2011 has been derived from the audited consolidated financial statements at that date.