Stockholders' Equity (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Oct. 27, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period			$ 137,390,000
Common stock options exercised			885,000
Stock-based compensation			622,000
Issuance of common stock, net of stock issuance costs of $2,246			31,861,000
Net income (loss)	$ 1,798,000	$ 798,000	2,223,000	$ 731,000
Dividends declared by joint ventures			(465,000)
Other comprehensive income	845,000	$ (2,036,000)	1,197,000	(1,709,000)
Balance, end of period	173,713,000		173,713,000		$ 137,390,000
Reclassification adjustment from AOCI			0	$ 0
Stock issuance cost			2,639,000
Stock repurchase program, authorized amount							$ 5,000,000
Shares repurchased (in shares)					0	908,000
Average price of shares repurchased (in dollars per share)						$ 2.52
Total purchase price						$ 2,300,000
Stock repurchase program remaining authorized repurchase amount	2,700,000		2,700,000
Preferred Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period			3,532,000
Common stock options exercised
Balance, end of period	3,532,000		3,532,000		$ 3,532,000
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period			33,000
Common stock options exercised			1,000
Issuance of common stock, net of stock issuance costs of $2,246			5,000
Balance, end of period	39,000		39,000		33,000
Additional Paid-In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period			194,177,000
Common stock options exercised			884,000
Stock-based compensation			622,000
Issuance of common stock, net of stock issuance costs of $2,246			31,856,000
Balance, end of period	227,539,000		227,539,000		194,177,000
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period			(64,985,000)
Net income (loss)			2,595,000
Balance, end of period	(62,390,000)		(62,390,000)		(64,985,000)
Accumulated Other Comprehensive Income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period			253,000
Other comprehensive income			1,040,000
Balance, end of period	1,293,000		1,293,000		253,000
AXT, Inc. Stockholders' Equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period			133,010,000
Common stock options exercised			885,000
Stock-based compensation			622,000
Issuance of common stock, net of stock issuance costs of $2,246			31,861,000
Net income (loss)			2,595,000
Other comprehensive income			1,040,000
Balance, end of period	170,013,000		170,013,000		133,010,000
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period			4,380,000
Net income (loss)			(372,000)
Dividends declared by joint ventures			(465,000)
Other comprehensive income			157,000
Balance, end of period	$ 3,700,000		$ 3,700,000		$ 4,380,000