Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Net sales	$ 265,950	$ 270,508	$ 252,458
Cost of sales	182,966	180,100	155,927
Gross profit	82,984	90,408	96,531
Operating expenses
Research and development	30,918	27,622	24,066
Selling, general and administrative	42,174	36,617	32,509
Impairment of goodwill	4,261	0	0
Total operating expenses	77,353	64,239	56,575
Operating income	5,631	26,169	39,956
Interest and other income, net	(1,656)	2,144	1,249
Interest expense	(68)	(88)	(57)
Gain on sale of investments, net	0	560	2,761
Income before income taxes	3,907	28,785	43,909
Provision (benefit) for income taxes	6,512	(27,338)	1,154
Consolidated net income (loss)	(2,605)	56,123	42,755
Less net income attributable to noncontrolling interests	(113)	(166)	(559)
Net income (loss) attributable to ISSI	$ (2,718)	$ 55,957	$ 42,196
Basic net income (loss) per share (in dollars per share)	$ (0.10)	$ 2.11	$ 1.65
Shares used in basic per share calculation (in shares)	27,120	26,568	25,603
Diluted net income (loss) per share (in dollars per share)	$ (0.10)	$ 1.98	$ 1.56
Shares used in diluted per share calculation (in shares)	27,120	28,308	27,041