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, 2009	$ 124,576	$ 2	$ 309,649	$ (185,481)	$ (1,344)	$ 122,826	$ 1,750
Common stock, shares, balance at Sep. 30, 2009		25,116,000
Components of comprehensive income (loss):
Net income (loss)	42,755			42,196		42,196	559
Change in cumulative translation adjustment, net of tax	1,839				1,839	1,839
Change in unrealized gain on investments, net of tax	(927)				(927)	(927)
Change in retirement plan obligations, net of tax	(1,854)				(1,854)	(1,854)
Total comprehensive income (loss)	41,813					41,254	559
Stock options exercised and shares issued upon vesting of restricted stock units (RSUs), shares		1,231,000
Stock options exercised and shares issued upon vesting of restricted stock units (RSUs), value	5,280	1	5,279			5,280
Shares issued under stock purchase plan, shares		116,000
Shares issued under stock purchase plan, value	687		687			687
Stock-based compensation	2,497		2,497			2,497
Shares repurchased and retired, shares		(246,000)
Shares repurchased and retired, value	(1,108)	0	(1,108)			(1,108)
Noncontrolling interest in Giantec	3,785		740			740	3,045
Change in noncontrolling interest in Wintram	291		29			29	262
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
Components of comprehensive income (loss):
Net income (loss)	56,123			55,957		55,957	166
Change in cumulative translation adjustment, net of tax	1,850				1,850	1,850
Change in unrealized gain on investments, net of tax	57				57	57
Change in retirement plan obligations, net of tax	(873)				(873)	(873)
Total comprehensive income (loss)	57,157					56,991	166
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), value	2,146	0	2,146			2,146
Shares issued under stock purchase plan, shares		167,000
Shares issued under stock purchase plan, value	1,239		1,239			1,239
Stock-based compensation	4,042		4,042			4,042
Shares repurchased and retired, shares	(500,000)	(509,000)
Shares repurchased and retired, value	(4,097)		(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	26,448,000
Components of comprehensive income (loss):
Net income (loss)	(2,605)			(2,718)		(2,718)	113
Change in cumulative translation adjustment, net of tax	3,932				3,932	3,932
Change in unrealized gain on investments, net of tax	(310)				(310)	(310)
Change in retirement plan obligations, net of tax	29				29	29
Total comprehensive income (loss)	1,046					933	113
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), value	4,439		4,439			4,439
Shares issued under stock purchase plan, shares		181,000
Shares issued under stock purchase plan, value	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, value	(537)		(537)			(537)
Change in noncontrolling interest in Wintram	71		8			8	63
Acquisition of noncontrolling interest in Wintram	(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