Condensed Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Net sales	$ 74,991	$ 62,505	$ 151,390	$ 128,669
Cost of sales	50,002	41,384	101,910	85,350
Gross profit	24,989	21,121	49,480	43,319
Operating expenses:
Research and development	10,308	6,506	20,331	14,107
Selling, general and administrative	10,730	9,418	21,819	18,915
Total operating expenses	21,038	15,924	42,150	33,022
Operating income	3,951	5,197	7,330	10,297
Interest and other income (expense), net	515	(194)	783	19
Gain on sale of investments	2,059	0	2,059	0
Income before income taxes	6,525	5,003	10,172	10,316
Provision for income taxes	3,245	1,406	4,404	2,950
Consolidated net income	3,280	3,597	5,768	7,366
Net loss attributable to noncontrolling interests	7	4	18	25
Net income attributable to ISSI	$ 3,287	$ 3,601	$ 5,786	$ 7,391
Basic net income per share (in dollars per share)	$ 0.12	$ 0.13	$ 0.21	$ 0.28
Shares used in basic per share calculation (in shares)	27,976	27,053	27,836	26,845
Diluted net income per share (in dollars per share)	$ 0.11	$ 0.12	$ 0.20	$ 0.26
Shares used in diluted per share calculation	29,348	28,913	29,240	28,642