Consolidated Statement 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, 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 (loss)	3,651				3,651	3,651
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		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
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated net income (loss)	17,744			17,548		17,548	196
Other comprehensive income (loss)	6,722				6,722	6,722
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)
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated net income (loss)	23,489			23,265		23,265	224
Other comprehensive income (loss)	(10,165)				(10,165)	(10,165)
Stock options exercised and shares issued upon vesting of restricted stock units (RSUs), shares		1,554,000
Stock options exercised and shares issued upon vesting of restricted stock units (RSUs)	10,042		10,042			10,042
Shares issued under stock purchase plan, shares		249,000
Shares issued under stock purchase plan	2,338		2,338			2,338
Stock-based compensation	6,092		6,092			6,092
Tax effects from employee stock incentive plans	2,581		2,581			2,581
Shares repurchased and retired, shares		(31,000)
Shares repurchased and retired	(358)		(358)			(358)
Payment of dividends to stockholders	(1,843)			(1,843)		(1,843)
Noncontrolling interest	(388)		(55)			(55)	(333)
Total stockholders' equity, balance at Sep. 30, 2014	$ 314,558	$ 3	$ 364,587	$ (51,076)	$ (1,044)	$ 312,470	$ 2,088
Common stock, shares, balance at Sep. 30, 2014	30,832,000	30,832,000