Condensed Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Net sales	$ 80,868	$ 74,991	$ 159,991	$ 151,390
Cost of sales	53,118	50,002	106,712	101,910
Gross profit	27,750	24,989	53,279	49,480
Operating expenses:
Research and development	10,827	10,308	21,385	20,331
Selling, general and administrative	11,469	10,730	22,903	21,819
Total operating expenses	22,296	21,038	44,288	42,150
Operating income	5,454	3,951	8,991	7,330
Interest and other income (expense), net	375	515	806	783
Gain on sale of investments	6,039	2,059	9,160	2,059
Income before income taxes	11,868	6,525	18,957	10,172
Provision for income taxes	2,910	3,245	4,553	4,404
Consolidated net income	8,958	3,280	14,404	5,768
Net (income) loss attributable to noncontrolling interests	(146)	7	(157)	18
Net income attributable to ISSI	$ 8,812	$ 3,287	$ 14,247	$ 5,786
Basic net income per share (in dollars per share)	$ 0.30	$ 0.12	$ 0.48	$ 0.21
Shares used in basic per share calculation	29,818	27,976	29,568	27,836
Diluted net income per share (in dollars per share)	$ 0.28	$ 0.11	$ 0.46	$ 0.20
Shares used in diluted per share calculation	31,244	29,348	30,986	29,240