Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Total ISSI Stockholders' Equity	Non-controlling Interest
Total stockholders' equity, balance at Sep. 30, 2010	$ 177,821	$ 3	$ 317,773	$ (143,285)	$ (2,286)	$ 172,205	$ 5,616
Common stock, shares, balance at Sep. 30, 2010		26,217,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated net income (loss)	56,123			55,957		55,957	166
Other comprehensive income	1,034				1,034	1,034
Stock options exercised and shares issued upon vesting of restricted stock units (RSUs), shares		573,000
Stock options exercised and shares issued upon vesting of restricted stock units (RSUs)	2,146	0	2,146			2,146
Shares issued under stock purchase plan, shares		167,000
Shares issued under stock purchase plan	1,239		1,239			1,239
Stock-based compensation	4,042		4,042			4,042
Shares repurchased and retired, shares		(509,000)
Shares repurchased and retired	(4,097)	0	(4,097)			(4,097)
Noncontrolling interest in Giantec	(3,364)		0			0	(3,364)
Change in noncontrolling interest in Wintram	302		28			28	274
Total stockholders' equity, balance at Sep. 30, 2011	235,246	3	321,131	(87,328)	(1,252)	232,554	2,692
Common stock, shares, balance at Sep. 30, 2011		26,448,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated net income (loss)	(2,605)			(2,718)		(2,718)	113
Other comprehensive income	3,651				3,651	3,651	0
Stock options exercised and shares issued upon vesting of restricted stock units (RSUs), shares		1,022,000
Stock options exercised and shares issued upon vesting of restricted stock units (RSUs)	4,439	0	4,439			4,439
Shares issued under stock purchase plan, shares		181,000
Shares issued under stock purchase plan	1,413		1,413			1,413
Stock-based compensation	5,031		5,031			5,031
Shares repurchased and retired, shares		(57,000)
Shares repurchased and retired	(537)		(537)			(537)
Change in noncontrolling interest in Wintram	71		8			8	63
Acquisition of noncontrolling interest	(2,370)		(1,012)			(1,012)	(1,358)
Noncontrolling interest in Chingis	1,996						1,996
Total stockholders' equity, balance at Sep. 30, 2012	246,335	3	330,473	(90,046)	2,399	242,829	3,506
Common stock, shares, balance at Sep. 30, 2012	27,594,000	27,594,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated net income (loss)	17,744			17,548		17,548	196
Other comprehensive income	6,722				6,722	6,722	0
Stock options exercised and shares issued upon vesting of restricted stock units (RSUs), shares		1,288,000
Stock options exercised and shares issued upon vesting of restricted stock units (RSUs)	6,264		6,264			6,264
Shares issued under stock purchase plan, shares		237,000
Shares issued under stock purchase plan	1,915		1,915			1,915
Stock-based compensation	5,941		5,941			5,941
Tax effects from employee stock incentive plans	18		18			18
Shares repurchased and retired, shares		(59,000)
Shares repurchased and retired	(555)		(555)			(555)
Acquisition of noncontrolling interest	1,614		109			109	1,505
Total stockholders' equity, balance at Sep. 30, 2013	$ 282,770	$ 3	$ 343,947	$ (72,498)	$ 9,121	$ 280,573	$ 2,197
Common stock, shares, balance at Sep. 30, 2013	29,060,000	29,060,000