Integrated Silicon Solution (ISSI) 10-Q 7 Aug 14 2014 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	Jun. 30, 2014	Aug. 01, 2014
Document and Entity Information [Abstract]	'	'
Entity Registrant Name	'INTEGRATED SILICON SOLUTION INC	'
Entity Central Index Key	'0000854701	'
Current Fiscal Year End Date	'--09-30	'
Entity Filer Category	'Accelerated Filer	'
Document Type	'10-Q	'
Document Period End Date	30-Jun-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Amendment Flag	'false	'
Entity Common Stock, Shares Outstanding	'	30,710,313

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Income (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Statement [Abstract]	'	'	'	'
Net sales	$84,834	$77,788	$244,825	$229,178
Cost of sales	55,538	51,741	162,250	153,651
Gross profit	29,296	26,047	82,575	75,527
Operating expenses:	'	'	'	'
Research and development	10,978	10,583	32,363	30,914
Selling, general and administrative	11,942	10,829	34,845	32,648
Total operating expenses	22,920	21,412	67,208	63,562
Operating income	6,376	4,635	15,367	11,965
Interest and other income (expense), net	99	546	905	1,329
Gain on sale of investments	2,140	7,280	11,300	9,339
Income before income taxes	8,615	12,461	27,572	22,633
Provision for income taxes	2,388	5,215	6,941	9,619
Consolidated net income	6,227	7,246	20,631	13,014
Net income attributable to noncontrolling interests	-41	-182	-198	-164
Net income attributable to ISSI	$6,186	$7,064	$20,433	$12,850
Basic net income per share (in dollars per share)	$0.20	$0.25	$0.69	$0.46
Shares used in basic per share calculation	30,312	28,293	29,816	27,988
Diluted net income per share (in dollars per share)	$0.19	$0.24	$0.65	$0.44
Shares used in diluted per share calculation	31,963	29,755	31,337	29,427

Condensed_Statement_of_Compreh

Condensed Statement of Comprehensive Income (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement of Comprehensive Income [Abstract]	'	'	'	'
Consolidated net income	$6,227	$7,246	$20,631	$13,014
Change in unrealized gain (loss) on investments:	'	'	'	'
Changes arising during current period, net of tax benefit (expense) of $0, ($2,750), $251 and ($9,774), respectively	0	7,231	-349	17,166
Reclassification for gain included in net income, net of tax expense of $592, $2,057, $3,589 and $2,193, respectively	-1,024	-2,371	-6,029	-3,039
Change in unrealized gain (loss) on investments:	-1,024	4,860	-6,378	14,127
Change in cumulative translation adjustment:	'	'	'	'
Changes arising during current period	2,989	-1,018	-1,020	-3,357
Change in retirement plan actuarial losses:	'	'	'	'
Reclassification for gain included in net income, net of tax expense (benefit) of $0 for the three and nine months ended June 30, 2014 and 2013	27	168	82	218
Change in retirement plan transition obligation:	'	'	'	'
Reclassification for gain included in net income, net of tax expense (benefit) of $0 for the three and nine months ended June 30, 2014 and 2013	-15	-67	-45	-97
Other comprehensive income (loss)	1,977	3,943	-7,361	10,891
Comprehensive income	8,204	11,189	13,270	23,905
Comprehensive income attributable to noncontrolling interest	-41	-182	-198	-164
Comprehensive income attributable to ISSI	$8,163	$11,007	$13,072	$23,741

Condensed_Statement_of_Compreh1

Condensed Statement of Comprehensive Income (Parenthetical) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement of Comprehensive Income [Abstract]	'	'	'	'
Unrealized gain (loss) on investments, Changes arising during current period, tax	$0	($2,750)	$251	($9,774)
Unrealized gain (loss) on investments, Reclassification for gain included in net income, tax	592	2,057	3,589	2,193
Retirement plan actuarial losses, Reclassification for gain included in net income, tax	0	0	0	0
Retirement plan transition obligation, Reclassification for gain included in net income, tax	$0	$0	$0	$0

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Jun. 30, 2014	Sep. 30, 2013
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$139,469	$119,997	[1]
Restricted cash	1,000	0	[1]
Short-term investments	1,746	21,558	[1]
Accounts receivable, net	50,329	46,088	[1]
Inventories	80,097	68,469	[1]
Deferred tax assets	2,840	2,326	[1]
Other current assets	15,745	14,602	[1]
Total current assets	291,226	273,040	[1]
Property, equipment and leasehold improvements, net	50,221	46,504	[1]
Purchased intangible assets, net	5,440	6,626	[1]
Goodwill	9,178	9,178	[1]
Deferred tax assets	10,338	9,942	[1]
Other assets	23,446	16,579	[1]
Total assets	389,849	361,869	[1]
Current liabilities:	'	'
Accounts payable	46,982	50,229	[1]
Accrued compensation and benefits	10,155	8,072	[1]
Accrued expenses	10,834	7,357	[1]
Current portion of long-term debt	195	195	[1]
Total current liabilities	68,166	65,853	[1]
Long-term debt	4,388	4,534	[1]
Other long-term liabilities	5,083	8,712	[1]
Total liabilities	77,637	79,099	[1]
Commitments and contingencies	'	'	[1]
Stockholders’ equity:	'	'
Common stock	3	3	[1]
Additional paid-in capital	360,293	343,947	[1]
Accumulated deficit	-52,065	-72,498	[1]
Accumulated other comprehensive income	1,760	9,121	[1]
Total ISSI stockholders’ equity	309,991	280,573	[1]
Noncontrolling interest	2,221	2,197	[1]
Total stockholders’ equity	312,212	282,770	[1]
Total liabilities and stockholders’ equity	$389,849	$361,869	[1]
[1]	Derived from audited financial statements.

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014		Jun. 30, 2013
Cash flows from operating activities	'		'
Consolidated net income	$20,631		$13,014
Adjustments to reconcile net income to net cash provided by operating activities:	'		'
Depreciation and amortization	5,885		4,152
Stock-based compensation	4,585		4,373
Excess tax benefits from share-based compensation	-2,567		0
Amortization of intangibles	1,186		1,191
Gain on sale of investments	-11,300		-9,339
Equity in net loss of affiliate	215		222
Net foreign currency transaction gains	-405		-538
Deferred tax assets	1,736		7,197
Other non-cash items	-35		56
Net effect of changes in current and other assets and current liabilities	-14,231		1,582
Net cash provided by operating activities	5,700		21,910
Cash flows from investing activities	'		'
Acquisition of property and equipment	-9,928		-17,883
Acquisition of noncontrolling interest in consolidated subsidiary	-199		-1,614
Payment of license fees	-7,098		0
Payment of holdback related to Si En acquisition	0		-4,200
Proceeds from sale of investments	0		4,256
Increase in restricted cash	-1,000		0
Purchases of available-for-sale securities	-1,316		-4,330
Sales of available-for-sale securities	22,143		22,637
Cash provided by (used in) investing activities	2,602		-1,134
Cash flows from financing activities	'		'
Repurchases and retirement of common stock	-350		-547
Proceeds from issuance of stock through compensation plans	9,569		5,338
Excess tax benefit from share-based compensation	2,567		0
Proceeds from borrowings	0		4,875
Principal payments of long-term obligations	-146		-97
Proceeds from borrowings under short-term lines of credit	0		4,069
Principal payments of short-term lines of credit	0		-4,069
Cash provided by financing activities	11,640		9,569
Effect of exchange rate changes on cash and cash equivalents	-470		-616
Net increase in cash and cash equivalents	19,472		29,729
Cash and cash equivalents at beginning of period	119,997	[1]	75,497
Cash and cash equivalents at end of period	$139,469		$105,226
[1]	Derived from audited financial statements.

Basis_of_Presentation

Basis of Presentation	9 Months Ended
	Jun. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Basis of Presentation	'
	Basis of Presentation
	The accompanying unaudited condensed consolidated financial statements include the accounts of Integrated Silicon Solution, Inc. (the Company or ISSI) and its consolidated majority owned subsidiaries, after elimination of all significant intercompany accounts and transactions. These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) for interim financial information and with Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by accounting principles generally accepted in the United States for complete financial statements. In the opinion of management, all adjustments (which are of a normal, recurring nature) considered necessary for fair presentation have been included.
	On September 14, 2012, the Company acquired approximately 94.1% of the outstanding shares of Chingis Technology Corporation (Chingis) and the Company’s financial results reflect accounting for Chingis on a consolidated basis from the date of acquisition. In May 2013, the Company acquired an additional 4.8% of Chingis for approximately $1.6 million. In October 2013, the Company acquired an additional 0.5% of Chingis for approximately $0.2 million. At June 30, 2014, the Company owned approximately 99.4% of the outstanding shares of Chingis.
	The Company’s operating results for the nine months ended June 30, 2014 are not necessarily indicative of the results that may be expected for the fiscal year ending September 30, 2014 or for any other period. The financial statements included herein should be read in conjunction with the Company’s Annual Report on Form 10-K for the fiscal year ended September 30, 2013.
	Certain reclassifications have been made to prior year balances in order to conform to the current year's presentation.

Use_of_Estimates

Use of Estimates	9 Months Ended
	Jun. 30, 2014
Accounting Policies [Abstract]	'
Use of Estimates	'
	Use of Estimates
	The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements as well as the reported amounts of revenues and expenses during the reporting period. Such estimates include the useful lives of fixed assets, allowances for doubtful accounts and customer returns, valuation allowances for deferred tax assets, inventory write-downs, potential reserves relating to litigation matters, accrued liabilities, and other reserves. The Company bases its estimates and judgments on its historical experience, knowledge of current conditions and its beliefs of what could occur in the future, given available information. Actual results may differ from those estimates, and such differences may be material to the financial statements.

Impact_of_Recently_Issued_Acco

Impact of Recently Issued Accounting Pronouncements and Standards	9 Months Ended
	Jun. 30, 2014
Accounting Changes and Error Corrections [Abstract]	'
Impact of Recently Issued Accounting Pronouncements and Standards	'
	Impact of Recently Issued Accounting Pronouncements and Standards
	The following issued accounting pronouncements are not yet effective for the Company as of June 30, 2014.
	Liabilities
	In February 2013, the Financial Accounting Standards Board (FASB) issued guidance for the recognition, measurement and disclosure of obligations resulting from joint and several liability arrangements for which the total amount of the obligation within the scope of the guidance is fixed at the reporting date. Examples of obligations include debt arrangements, other contractual obligations, and settled litigation and judicial rulings. The guidance requires an entity to measure such obligations as the sum of the amount that the reporting entity agreed to pay on the basis of its arrangement among its co-obligors in addition to amounts the reporting entity expects to pay on behalf of its co-obligors. The guidance becomes effective for the Company beginning in the first quarter of fiscal 2015 and is not expected to have a material impact on the Company's consolidated financial statements.
	Foreign Currency Matters
	In March 2013, FASB issued guidance on when foreign currency translation adjustments should be released to net income. When a parent entity ceases to have a controlling financial interest in a subsidiary or group of assets that is a business within a foreign entity, the parent is required to release any related cumulative translation adjustment into net income. Accordingly, the cumulative translation adjustment should be released into net income only if the sale or transfer results in the complete or substantially complete liquidation of the foreign entity in which the subsidiary or group of assets had resided. The guidance becomes effective for the Company beginning in the first quarter of fiscal 2015 and is not expected to have a material impact on the Company's consolidated financial statements.
	Revenue from Contracts with Customers
	In May 2014, FASB amended the existing accounting standards for revenue recognition. The new guidance establishes principles for recognizing revenue upon the transfer of promised goods or services to customers, in an amount that reflects the expected consideration received in exchange for those goods or services. The guidance becomes effective for the Company beginning in the first quarter of fiscal 2018. Early adoption is not permitted. The new revenue standard may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of adoption. The Company has not yet selected a transition method nor has the Company determined the impact of adopting the new revenue standard on its consolidated financial statements.

Fair_Value_Measurements

Fair Value Measurements	9 Months Ended
	Jun. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	Fair Value Measurements
	Under FASB guidance, fair value is defined as the price expected to be received from the sale of an asset or paid to transfer a liability in a transaction between market participants at the measurement date. In determining fair value, the Company uses various valuation approaches, including quoted market prices and discounted cash flows. The FASB guidance also establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs are inputs that the market participants would use in pricing the asset or liability developed based on market data obtained from independent sources. Unobservable inputs are inputs that reflect a company’s judgment concerning the assumptions that market participants would use in pricing the asset or liability developed based on the best information available at that time. The fair value hierarchy is broken down into the following three levels based on the reliability of inputs:
	•	Level 1 – Valuations based on quoted prices in active markets for identical instruments that the Company is able to access. Since valuations are based on quoted prices which are readily and regularly available in an active market, valuation of these products can be done without a significant degree of judgment.
	•	Level 2 – Valuations based on quoted prices in active markets for instruments that are similar, or quoted prices in markets that are not active for identical or similar instruments and model-derived valuations in which all significant inputs and significant value drives are observable in active markets.
	•	Level 3 – Valuations based on inputs that are unobservable and significant to the overall fair value measurement. These values are generally determined using pricing models for which the assumptions utilize management’s estimates of market participant assumptions.
	As of June 30, 2014 and September 30, 2013, all of the Company’s financial assets utilize Level 1 inputs. The Company did not have any financial assets utilizing Level 2 or Level 3 inputs at June 30, 2014 or September 30, 2013.
	The following table represents the Company’s fair value hierarchy for financial assets measured at fair value on a recurring basis:
			June 30,			September 30,
			2014			2013
			(Level 1)			(Level 1)
			(In thousands)
	Money market instruments (1)		$	19,321		$	19,318
	Semiconductor Manufacturing International Corp.
	(SMIC) common stock (2)		—			1,793
	Nanya Technology Corporation (Nanya) common stock (2)		—			16,624
			$	19,321		$	37,735
	-1	Included in cash and cash equivalents
	-2	Included in short-term investments
	There were no transfers in or out of Level 1 assets during the three months ended June 30, 2014.
	As of June 30, 2014, the Company did not have any liabilities or non-financial assets that are measured at fair value on a recurring basis.
	Available-for-sale marketable securities consisted of the following:
	June 30, 2014		Amortized			Gross		Gross		Fair
			Cost			Unrealized		Unrealized		Value
						Holding		Holding
						Gains		Losses
						(In thousands)
	Money market instruments		$	19,321		$	—	$	—	$	19,321
	Certificates of deposit		21,266			—		—		21,266
	Nanya common stock		—			—		—		—
	Total		40,587			—		—		40,587
	Less: Amounts included in cash, cash
	equivalents and restricted cash		(38,841		)	—		—		(38,841		)
			$	1,746		$	—	$	—	$	1,746
	September 30, 2013		Amortized			Gross		Gross		Fair
			Cost			Unrealized		Unrealized		Value
						Holding		Holding
						Gains		Losses
						(In thousands)
	Money market instruments		$	19,318		$	—	$	—	$	19,318
	Certificates of deposit		15,595			—		—		15,595
	SMIC common stock		1,099			694		—		1,793
	Nanya common stock		7,100			9,524		—		16,624
	Total		43,112			10,218		—		53,330
	Less: Amounts included in cash and cash
	equivalents		(31,772		)	—		—		(31,772		)
			$	11,340		$	10,218	$	—	$	21,558
	During the three months ended June 30, 2014, the Company sold its approximately 23.2 million remaining shares of freely- tradeable Nanya common stock for approximately $3.6 million which resulted in a pre-tax gain of approximately $2.1 million. During the nine months ended June 30, 2014, the Company sold approximately 109.6 million shares of Nanya common stock for approximately $16.2 million which resulted in a pre-tax gain of approximately $9.2 million. See Note 8 for further information regarding our Nanya share ownership.
	During the nine months ended June 30, 2014, the Company sold all of its approximately 29.9 million remaining shares of SMIC common stock for approximately $3.2 million which resulted in a pre-tax gain of approximately $2.1 million.
	As of June 30, 2014 and September 30, 2013, the Company had cash, cash equivalents, restricted cash and short-term investments in foreign financial institutions of $70.2 million ($2.0 million of which was in China and subject to exchange control regulations) and $71.2 million, respectively.

Stockbased_Compensation

Stock-based Compensation	9 Months Ended
	Jun. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Stock-based Compensation	'
	Stock-based Compensation
	Stock-Based Benefit Plans
	The Company grants stock-based compensation awards under its 2007 Incentive Compensation Plan (the 2007 Plan) which permits the grant of stock options, stock appreciation rights (SARs), restricted stock awards, restricted stock units (RSUs), performance shares and performance units. The Company has outstanding grants under its 2012 Inducement Option Plan (the Inducement Plan) and under prior plans, though no further grants can be made under these plans. At June 30, 2014, 1,811,000 shares were available for future grant under the 2007 Plan. Options generally vest ratably over a four-year period with a 6-month or 1-year cliff vest and then vesting ratably over the remaining period. Options granted prior to October 1, 2005 expire ten years after the date of grant; options granted after October 1, 2005 expire seven years after the date of the grant. RSUs generally vest annually over periods ranging from two years to four years based upon continued employment with the Company.
	The Company began granting cash-settled SARs in the first quarter of fiscal 2014. The SARs vest ratably over a four-year period with a 6-month or 1-year cliff vest and then vest ratably each month over the remaining period based upon continued employment with the Company. The SARs expire seven years after the date of grant. These SARs allow the holder to receive in cash the difference between the SARs' exercise price (which is the closing market price of the Company's common stock on the grant date) and the closing market price of the Company's common stock on the date the holder exercises the SAR. The SARs are recorded as a liability in accrued compensation and benefits in the Company's balance sheet.
	The Company has an Employee Stock Purchase Plan (ESPP) which permits eligible employees to purchase shares of the Company’s common stock through payroll deductions. As approved by the Board of Directors, effective August 1, 2010, shares under the ESPP are purchased at a price equal to 85% of the lesser of the fair market value of the Company’s common stock as of the first day or the last day of each six-month offering period. The offering periods under the ESPP commence on approximately February 1 and August 1 of each year. At June 30, 2014, 453,000 shares were available for future issuance under the ESPP.
	Stock-Based Compensation
	The following table outlines the effects of total stock-based compensation including expense related to SARs.
		Three Months Ended								Nine Months Ended
		June 30,								June 30,
		2014				2013				2014			2013
					(In thousands)
	Stock-based compensation
	Cost of sales	$	50			$	46			$	154		$	133
	Research and development	694				566				2,119			1,665
	Selling, general and administrative	1,017				852				3,156			2,575
	Total stock-based compensation	1,761				1,464				5,429			4,373
	Tax effect on stock-based compensation	(330		)		—				(1,018		)	—
	Net effect on net income	$	1,431			$	1,464			$	4,411		$	4,373
	Compensation related to SARs included in total stock-based compensation	$	222			$	—			$	844		$	—
	As of June 30, 2014, there was approximately $9.4 million of total unrecognized stock-based compensation expense related to options and awards under the Company’s stock-based benefit plans that will be recognized over a weighted-average period of approximately 2.23 years. Future stock option and award grants will add to this total whereas quarterly amortization and the vesting of the existing stock option and award grants will reduce this total. In addition, as of June 30, 2014, there was approximately $54,000 of total unrecognized stock-based compensation expense under the Company’s ESPP that will be recognized over a weighted-average period of approximately one month. As of June 30, 2014, there was approximately $4.4 million of total unrecognized stock-based compensation expense related to SARs that will be recognized over a weighted-average period of approximately 3.36 years. Future SAR grants will add to this total whereas quarterly amortization and the vesting of the SARs will reduce this total. In addition, because the SARs are settled with cash, the fair value of the SARs must be revalued on a quarterly basis which will likely impact the amount of expense in future periods.
	The Company uses the Black-Scholes option pricing model to estimate the fair value of the options and SARS granted and rights to acquire stock granted under the ESPP. The weighted average estimated fair values of stock option grants and rights granted under the ESPP, as well as the weighted average assumptions used in calculating these values during the three and nine month periods ended June 30, 2014 and 2013 were based on estimates at the date of grant as follows:
		Three Months Ended								Nine Months Ended
		June 30,								June 30,
		2014				2013				2014			2013
	Options
	Weighted-average fair value of grants	$	6.13			$	4.31			$	4.7		$	4.31
	Expected term in years	4.42				4.45				4.42			4.45
	Estimated volatility	51		%		55		%		51		%	59		%
	Risk-free interest rate	1.21		%		0.62		%		1.04		%	0.53		%
	Dividend yield	—		%		—		%		—		%	—		%
	ESPP
	Weighted-average fair value of grants	$	—			$	—			$	2.66		$	2.3
	Expected term in years	—				—				0.49			0.49
	Estimated volatility	—		%		—		%		27		%	32		%
	Risk-free interest rate	—		%		—		%		0.41		%	0.11		%
	Dividend yield	—		%		—		%		—		%	—		%
	The Company issues RSUs from time to time. The estimated fair value of RSU awards is calculated based on the market price of the Company’s common stock on the date of grant. The weighted average grant date fair value of RSUs granted in the three month period ended June 30, 2014 was $14.45 per share. The weighted average grant date fair value of RSUs granted in the nine month periods ended June 30, 2014 and June 30, 2013, was $11.62 per share and $9.14 per share, respectively.
	A summary of the Company’s stock option activity and related information for the nine months ended June 30, 2014 follows (number of shares and aggregate intrinsic value are presented in thousands):
		Number of			Weighted-Average				Weighted-Average		Aggregate
		Shares			Exercise Price				Remaining		Intrinsic Value
									Contractual Term in Years
	Outstanding at September 30, 2013	5,351			$	7.51
	Granted	468			$	11.22
	Exercised	(1,239	)		$	6.77					$	7,632
	Cancelled/Expired	(121	)		$	10.18
	Outstanding at June 30, 2014	4,459			$	8.03			3.94		$	30,036
	Exercisable at June 30, 2014	2,759			$	6.87			3.13		$	21,800
	Vested and expected to vest after June 30, 2014	4,384			$	8			3.91		$	29,689
	A summary of the Company’s RSU activity and related information for the nine months ended June 30, 2014 under the 2007 Plan follows (number of shares and aggregate intrinsic value are presented in thousands):
		Number of			Weighted-Average				Aggregate
		Shares			Grant Date				Intrinsic Value
					Fair Value
	Outstanding at September 30, 2013	269			$	9.02
	Granted	88			$	11.62
	Vested	(92	)		$	8.91			$	1,062
	Forfeited	(1	)		$	10.64
	Outstanding at June 30, 2014	264			$	9.92			$	3,899
	A summary of the Company’s SAR activity and related information for the nine months ended June 30, 2014 under the 2007 Plan follows (number of shares and aggregate intrinsic value are presented in thousands):
		Number of			Weighted-Average				Weighted-Average		Aggregate
		Shares			Exercise Price				Remaining		Intrinsic Value
									Contractual Term in Years
	Outstanding at September 30, 2013	—			$	—
	Granted	779			$	10.96
Exercised	(3	)		$	10.96
Cancelled/Expired	(18	)		$	10.96
Outstanding at June 30, 2014	758			$	10.96			6.32		$	2,889
Exercisable at June 30, 2014	62			$	10.96			6.28		$	237

Concentrations

Concentrations	9 Months Ended
	Jun. 30, 2014
Risks and Uncertainties [Abstract]	'
Concentrations	'
	Concentrations
	In the three and nine months ended June 30, 2014, revenue from the Company's largest distributor accounted for approximately 20% and 18%, respectively, of the Company's total net sales. In the three and nine months ended June 30, 2014, revenue from the Company's second largest distributor accounted for approximately 12% and 13%, respectively, of the Company's total net sales. In the three and nine months ended June 30, 2013, revenue from the Company's largest distributor accounted for approximately 13% and 14%, respectively, of the Company's total net sales. In the three and nine months ended June 30, 2013, revenue from the Company's second largest distributor accounted for approximately 10% and 11%, respectively, of the Company's total net sales.

Inventories

Inventories	9 Months Ended
	Jun. 30, 2014
Inventory Disclosure [Abstract]	'
Inventories	'
	Inventories
	The following is a summary of inventories by major category:
		June 30,		September 30,
		2014		2013
		(In thousands)
	Purchased components	$	18,193	$	14,039
	Work-in-process	27,570		20,960
	Finished goods	34,334		33,470
		$	80,097	$	68,469
	During the three and nine months ended June 30, 2014, the Company recorded inventory write-downs of $2.1 million and $4.3 million, respectively. During the three and nine months ended June 30, 2013, the Company recorded inventory write-downs of $1.2 million and $3.5 million, respectively. The inventory write-downs were predominantly for excess and obsolescence and lower of cost or market issues on certain of the Company's products.

Other_Assets

Other Assets	9 Months Ended
	Jun. 30, 2014
Other Assets [Abstract]	'
Other Assets	'
	Other Assets
	Other assets consisted of the following:
		June 30,		September 30,
		2014		2013
		(In thousands)
	Restricted assets	$	508	$	811
	Other investment	1,469		1,684
	Nanya private placement shares	10,831		10,920
	Technology licenses, net	9,456		2,002
	Other	1,182		1,162
		$	23,446	$	16,579
	The Company has various deposits including deposits with suppliers for purchase guarantees and for customs clearance. These deposits are included in restricted assets.
	In September 2012, the Company invested approximately $27.1 million in Nanya, which was comprised of common shares which are classified as available-for-sale securities and private placement shares which are accounted for on the cost-basis. The Company accounts for the private placement shares it acquired in Nanya on the cost-basis as these securities are restricted and the restrictions do not terminate within one year of the reporting date. In addition, as of June 30, 2014, the Company had pledged $5.3 million of its Nanya private placement shares as collateral for the Company's accounts payable.
	From time-to-time, the Company licenses patents or other intellectual property rights from third parties. The technology licenses are being amortized over their estimated useful lives ranging from three to ten years.
	In March 2012, the Company made an equity investment of $2.0 million in a private technology company headquartered in Hong Kong. At June 30, 2014, the Company's ownership interest in such company was approximately 31%. This investment is accounted for under the equity method and the Company's results include its percentage share of such company's results of operations in interest and other income, net.

Purchased_Intangible_Assets

Purchased Intangible Assets	9 Months Ended
	Jun. 30, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Purchased Intangible Assets	'
	Purchased Intangible Assets
	The following tables present details of the Company’s total purchased intangible assets:
			Gross		Accumulated		Net
					Amortization
			(In thousands)
	June 30, 2014
	Developed technology		$	5,330	$	2,414	$	2,916
	Customer relationships		3,340		997		2,343
	Other		450		269		181
	Total		$	9,120	$	3,680	$	5,440
	September 30, 2013
	Developed technology		$	5,330	$	1,758	$	3,572
	Customer relationships		3,340		580		2,760
	Other		450		156		294
	Total		$	9,120	$	2,494	$	6,626
	The following table presents details of the amortization expense of purchased intangible assets as reported in the consolidated statements of income:
			Three Months Ended				Nine Months Ended
			June 30,				June 30,
			2014		2013		2014		2013
			(In thousands)
	Reported as:
	Cost of sales		$	191	$	222	$	656	$	647
	Operating expenses		177		176		530		544
	Total		$	368	$	398	$	1,186	$	1,191
	The following table presents the estimated future amortization expense of the Company’s purchased intangible assets at June 30, 2014 (in thousands). The weighted-average remaining amortization period for developed technology, customer relationships and other intangibles is 4.29 years, 4.21 years and 1.21 years, respectively. If the Company acquires additional purchased intangible assets in the future, its future amortization may be increased by those assets.
	Fiscal year
	Remainder of 2014	$	347
	2015	1,382
	2016	1,238
	2017	1,239
	2018	1,195
	Thereafter	39
	Total	$	5,440

Borrowings

Borrowings	9 Months Ended
	Jun. 30, 2014
Debt Disclosure [Abstract]	'
Borrowings	'
	Borrowings
	In December 2012, the Company obtained a bank loan in the amount of $4.9 million (the Loan), to partially finance the $6.5 million purchase price of approximately 2.85 acres of land and a 55,612 square foot building located at 1623 Buckeye Drive, Milpitas, California for its corporate headquarters. The Loan has a maturity date of November 30, 2017 and is secured by the property and an assignment of all leases and rents relating to the property. The Loan is subject to customary events of default, including defaults in the payment of principal and interest. The Loan bears an interest rate of one percent above LIBOR adjusted on a monthly basis. Principal payments due under the Loan are as follows (in thousands):
	Fiscal year
	Remainder of 2014	$	49
	2015	195
	2016	195
	2017	195
	2018	195
	Thereafter	3,754
	Total	$	4,583

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income	9 Months Ended
	Jun. 30, 2014
Stockholders' Equity Note [Abstract]	'
Accumulated Other Comprehensive Income	'
	Accumulated Other Comprehensive Income
	The components of accumulated other comprehensive income, net of tax, were as follows:
		June 30,			September 30,
		2014			2013
		(In thousands)
	Accumulated foreign currency translation adjustments	$	3,767		$	4,787
	Accumulated net unrealized gain on SMIC (net of tax of $0 and $275, respectively)	—			419
	Accumulated net unrealized gain on Nanya (net of tax of $0 and $3,565, respectively)	—			5,959
	Accumulated net retirement plan transition asset (net of tax of $148 and $148, respectively)	2			47
	Accumulated net retirement plan actuarial losses (net of tax of $470 and $470, respectively)	(2,009		)	(2,091		)
	Total accumulated other comprehensive income	$	1,760		$	9,121
	The significant amounts reclassified out of accumulated other comprehensive income into the consolidated condensed statements of income, with presentation location, during the three and nine months ended June 30, 2014 and June 30, 2013 were as follows:
		Three Months Ended						Nine Months Ended
		June 30,						June 30,
		2014			2013			2014			2013
		(In thousands)
	Comprehensive Income Components	Amount Reclassified from Accumulated Other Comprehensive Income						Amount Reclassified from Accumulated Other Comprehensive Income						Location
	Unrealized holding gains (losses) on available-for -sale investments
		$	1,616		$	4,428		$	9,618		$	5,232		Gain on the sale of investments
		(592		)	(2,057		)	(3,589		)	(2,193		)	Provision for income taxes
		$	1,024		$	2,371		$	6,029		$	3,039

Income_Taxes

Income Taxes	9 Months Ended
	Jun. 30, 2014
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	Income Taxes
	The income tax provision includes U.S. federal, state and local, and foreign income taxes and is based on the application of a forecasted annual income tax rate applied to the current quarter's year-to-date pre-tax income for fiscal 2014. In determining the estimated annual effective income tax rate, the Company analyzes various factors, including projections of the Company's annual earnings, taxing jurisdictions in which the earnings will be generated, the impact of state and local income taxes, the Company's ability to use tax credits and net operating loss carryforwards, and available tax planning alternatives. Discrete items, including the effect of changes in tax laws, tax rates, and certain circumstances with respect to valuation allowances or other unusual or non-recurring tax adjustments are reflected in the period in which they occur as an addition to, or reduction from, the income tax provision, rather than being included in the estimated annual effective income tax rate.
	For the three and nine months ended June 30, 2014, the Company recorded income tax expense of $2.4 million and $6.9 million, respectively, that represents an effective tax rate of approximately 28% and 25%, respectively. The differences between the recorded provision for income taxes and the tax provision, based on the federal statutory rate of 35%, were primarily attributable to the differential in foreign tax rates, non-deductible stock-based compensation expense and certain foreign losses not benefited.
	For the three months and nine months ended June 30, 2013, the Company recorded income tax expense of $5.2 million and $9.6 million, respectively, that represents an effective tax rate of approximately 42% and 42%, respectively. Discrete items were recorded in the three months and nine months ended June 30, 2013 related to a decrease in the valuation allowance of approximately $1.3 million for foreign tax credit carryforwards based on the Company's estimated ability to use these carryforwards in the future as a result of a change in its legal structure and an increase in the valuation allowance for research and development credits of $0.5 million in certain foreign jurisdictions based on the Company's estimated inability to use these credits in the future. The nine months ended June 30, 2013 includes an additional discrete item related to an increase in the valuation allowance of approximately $1.5 million for California net operating loss carryforwards based on the Company's estimated inability to use these carryforwards in the future as a result of a change in the Company's legal structure. The difference between the recorded provision for income taxes and the tax provision, based on the federal statutory rate of 35%, was primarily attributable to the impact of these discrete items, the differential in foreign tax rates, significant foreign inclusions and non-deductible stock-based compensation expense.
	As of June 30, 2014, the Company had unrecognized tax positions that would impact its effective tax rate, if realized.

Per_Share_Data

Per Share Data	9 Months Ended
	Jun. 30, 2014
Earnings Per Share [Abstract]	'
Per Share Data	'
	Per Share Data
	The following table sets forth the computation of basic and diluted net income per share (in thousands, except per share amounts):
		Three Months Ended				Nine Months Ended
		June 30,				June 30,
		2014		2013		2014		2013
	Numerator for basic and diluted net income per share:
	Net income attributable to ISSI	$	6,186	$	7,064	$	20,433	$	12,850
	Denominator for basic net income per share:
	Weighted average common shares outstanding	30,312		28,293		29,816		27,988
	Dilutive stock options and awards	1,651		1,462		1,521		1,439
	Denominator for diluted net income per share	31,963		29,755		31,337		29,427
	Basic net income per share	$	0.2	$	0.25	$	0.69	$	0.46
	Diluted net income per share	$	0.19	$	0.24	$	0.65	$	0.44
	For the three months and nine months ended June 30, 2014, stock options and awards for 686,000 shares and 1,070,000 shares, respectively, were excluded from diluted earnings per share by the application of the treasury stock method. For the three months and nine months ended June 30, 2013, stock options and awards for 2,864,000 shares and 2,849,000 shares, respectively, were excluded from diluted earnings per share by the application of the treasury stock method.

Common_Stock_Repurchase_Progra

Common Stock Repurchase Program	9 Months Ended
	Jun. 30, 2014
Common Stock Repurchase Program [Abstract]	'
Common Stock Repurchase Program	'
	Common Stock Repurchase Program
	In the nine month period ended June 30, 2014, the Company did not repurchase any shares of its common stock in the open market. As of June 30, 2014, the Company had repurchased and retired an aggregate of 14,179,711 shares of common stock at a cost of approximately $88.5 million since September 2007. As of June 30, 2014, $19.8 million remained available under the Company's existing share repurchase authorization.
	The Company issues RSUs as part of its equity incentive plan. For a portion of the RSUs granted, the number of shares issued on the date the RSUs vest is net of the statutory withholding requirements that the Company pays on behalf of its employees. During the nine months ended June 30, 2014, the Company withheld 30,323 shares to satisfy approximately $0.4 million of employee tax obligations. Although the shares withheld are not issued, they are treated as common stock repurchases for accounting purposes, as they reduce the number of shares that would have been issued upon vesting.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Jun. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	Commitments and Contingencies
	Legal Matters
	In the semiconductor industry, it is not unusual for companies to receive notices alleging infringement of patents or other intellectual property rights of others. The Company has been, and from time-to-time expects to be, notified of claims that it may be infringing patents, maskwork rights or copyrights owned by third parties. If it appears necessary or desirable, the Company may seek licenses under patents that it is alleged to be infringing. Although patent holders commonly offer such licenses, licenses may not be offered and the terms of any offered licenses may not be acceptable to the Company. The failure to obtain a license under a key patent or intellectual property right from a third party for technology used by the Company could cause it to incur substantial liabilities and to suspend the manufacture of the products utilizing the invention or to attempt to develop non-infringing products, any of which could materially and adversely affect the Company’s business and operating results. Furthermore, there can be no assurance that the Company will not become involved in protracted litigation regarding its alleged infringement of third party intellectual property rights or litigation to assert and protect its patents or other intellectual property rights. Any litigation relating to patent infringement or other intellectual property matters could result in substantial cost and diversion of the Company’s resources.
	GSI Technology Inc. v. Integrated Silicon Solution, Inc., et al.
	On October 2, 2013, GSI Technology Inc. (GSI) filed a Second Amended Complaint in a lawsuit filed earlier in 2013 solely against defendant United Memories, Inc. in the United States District Court for the Northern District of California.  GSI named the Company as a new, second defendant in the Second Amended Complaint.  On April 18, 2014, the Court granted the Company's motion to dismiss that complaint in part, leaving claims against the Company for Unfair Competition under California Business & Professions Code 17200, misappropriation of trade secrets, and intentional interference with prospective economic advantage.  In the remaining portion of the complaint, GSI alleges that the Company acted together with United Memories, Inc. to harm GSI in connection with a bid from Cisco Systems, Inc. and misappropriated alleged GSI trade secrets.  GSI seeks damages and injunctive relief.  The Company filed an answer on June 2, 2014 and asserted a declaratory relief counterclaim against GSI.  Before the Company was named as a defendant, the Court denied motions by GSI against United Memories, Inc. for temporary and preliminary injunctive relief.  The Court issued a case management order on June 13, 2014 with a scheduled trial date of July 13, 2015.   The Company believes it has meritorious defenses to the claims alleged by GSI and intends to defend this suit vigorously.  However, there can be no assurance as to the outcome of this matter or any future litigation.
	Other Legal Proceedings
	In the ordinary course of its business, the Company has been involved in a limited number of other legal actions, both as plaintiff and defendant, and could incur uninsured liability in any one or more of them. Although the outcome of these actions is not presently determinable, the Company believes that the ultimate resolution of these matters will not have a material adverse effect on its financial position, cash flows or results of operations. However, no assurances can be given with respect to the extent or outcome of any such litigation in the future.
	Commitments to Wafer Fabrication Facilities and Contract Manufacturers
	The Company issues purchase orders for wafers to various wafer foundries. These purchase orders are generally considered to be cancelable. However, to the degree that the wafers have entered into work-in-process at the foundry, as a matter of practice, it becomes increasingly difficult to cancel the purchase order. As of June 30, 2014, the Company had approximately $26.6 million of purchase orders for which the related wafers had been entered into wafer work-in-process (i.e., manufacturing had begun).

Geographic_and_Segment_Informa

Geographic and Segment Information	9 Months Ended
	Jun. 30, 2014
Segment Reporting [Abstract]	'
Geographic and Segment Information	'
	Geographic and Segment Information
	The Company has one operating segment, which is to design, develop, and market high-performance SRAM, DRAM, and other semiconductor products. The following table summarizes the Company’s operations in different geographic areas:
		Three Months Ended				Nine Months Ended
		June 30,				June 30,
		2014		2013		2014		2013
				(In thousands)
	Net sales
	United States	$	9,571	$	9,517	$	28,449	$	27,731
	China	9,838		10,477		32,689		20,579
	Hong Kong	16,456		13,638		45,499		50,532
	Japan	5,916		8,194		16,569		23,241
	Korea	4,000		3,311		10,544		10,064
	Taiwan	12,344		11,230		35,099		30,447
	Other Asia Pacific countries	6,435		5,880		18,390		18,374
	Europe	19,587		14,797		56,207		46,681
	Other	687		744		1,379		1,529
	Total net sales	$	84,834	$	77,788	$	244,825	$	229,178
		June 30,		September 30,
		2014		2013
		(In thousands)
	Long-lived assets
	United States	$	10,943	$	9,696
	Hong Kong	16		7
	China	3,955		3,424
	Taiwan	35,307		33,377
		$	50,221	$	46,504
	Revenues are attributed to countries based on the customers' ship-to location.
	Long-lived assets by geographic area are those assets used in the Company’s operations in each area.

Related_Party_Transactions

Related Party Transactions	9 Months Ended
	Jun. 30, 2014
Related Party Transactions [Abstract]	'
Related Party Transactions	'
	Related Party Transactions
	The Company sells semiconductor products to Chrontel International Ltd. (Chrontel). Jimmy S.M. Lee, the Company’s Executive Chairman, has been a director of Chrontel since July 1995. Sales to Chrontel were $80,000 and $162,000 during the three months and nine months ending June 30, 2014, respectively. Sales to Chrontel were $104,000 and $294,000 during the three months and nine months ending June 30, 2013, respectively. Accounts receivable from Chrontel was approximately $26,000 and $65,000 at June 30, 2014 and September 30, 2013, respectively.

Basis_of_Presentation_Policies

Basis of Presentation (Policies)	9 Months Ended
	Jun. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Basis of Presentation	'
	Basis of Presentation
	The accompanying unaudited condensed consolidated financial statements include the accounts of Integrated Silicon Solution, Inc. (the Company or ISSI) and its consolidated majority owned subsidiaries, after elimination of all significant intercompany accounts and transactions. These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) for interim financial information and with Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by accounting principles generally accepted in the United States for complete financial statements. In the opinion of management, all adjustments (which are of a normal, recurring nature) considered necessary for fair presentation have been included.
Accounting Pronouncements	'
	The following issued accounting pronouncements are not yet effective for the Company as of June 30, 2014.
	Liabilities
	In February 2013, the Financial Accounting Standards Board (FASB) issued guidance for the recognition, measurement and disclosure of obligations resulting from joint and several liability arrangements for which the total amount of the obligation within the scope of the guidance is fixed at the reporting date. Examples of obligations include debt arrangements, other contractual obligations, and settled litigation and judicial rulings. The guidance requires an entity to measure such obligations as the sum of the amount that the reporting entity agreed to pay on the basis of its arrangement among its co-obligors in addition to amounts the reporting entity expects to pay on behalf of its co-obligors. The guidance becomes effective for the Company beginning in the first quarter of fiscal 2015 and is not expected to have a material impact on the Company's consolidated financial statements.
	Foreign Currency Matters
	In March 2013, FASB issued guidance on when foreign currency translation adjustments should be released to net income. When a parent entity ceases to have a controlling financial interest in a subsidiary or group of assets that is a business within a foreign entity, the parent is required to release any related cumulative translation adjustment into net income. Accordingly, the cumulative translation adjustment should be released into net income only if the sale or transfer results in the complete or substantially complete liquidation of the foreign entity in which the subsidiary or group of assets had resided. The guidance becomes effective for the Company beginning in the first quarter of fiscal 2015 and is not expected to have a material impact on the Company's consolidated financial statements.
	Revenue from Contracts with Customers
	In May 2014, FASB amended the existing accounting standards for revenue recognition. The new guidance establishes principles for recognizing revenue upon the transfer of promised goods or services to customers, in an amount that reflects the expected consideration received in exchange for those goods or services. The guidance becomes effective for the Company beginning in the first quarter of fiscal 2018. Early adoption is not permitted. The new revenue standard may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of adoption. The Company has not yet selected a transition method nor has the Company determined the impact of adopting the new revenue standard on its consolidated financial statements.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	9 Months Ended
	Jun. 30, 2014
Fair Value Disclosures [Abstract]	'
Assets Measured on Recurring Basis	'
	The following table represents the Company’s fair value hierarchy for financial assets measured at fair value on a recurring basis:
			June 30,			September 30,
			2014			2013
			(Level 1)			(Level 1)
			(In thousands)
	Money market instruments (1)		$	19,321		$	19,318
	Semiconductor Manufacturing International Corp.
	(SMIC) common stock (2)		—			1,793
	Nanya Technology Corporation (Nanya) common stock (2)		—			16,624
			$	19,321		$	37,735
	-1	Included in cash and cash equivalents
	-2	Included in short-term investments
Available-for-sale Securities	'
	Available-for-sale marketable securities consisted of the following:
	June 30, 2014		Amortized			Gross		Gross		Fair
			Cost			Unrealized		Unrealized		Value
						Holding		Holding
						Gains		Losses
						(In thousands)
	Money market instruments		$	19,321		$	—	$	—	$	19,321
	Certificates of deposit		21,266			—		—		21,266
	Nanya common stock		—			—		—		—
	Total		40,587			—		—		40,587
	Less: Amounts included in cash, cash
	equivalents and restricted cash		(38,841		)	—		—		(38,841		)
			$	1,746		$	—	$	—	$	1,746
	September 30, 2013		Amortized			Gross		Gross		Fair
			Cost			Unrealized		Unrealized		Value
						Holding		Holding
						Gains		Losses
						(In thousands)
	Money market instruments		$	19,318		$	—	$	—	$	19,318
	Certificates of deposit		15,595			—		—		15,595
	SMIC common stock		1,099			694		—		1,793
	Nanya common stock		7,100			9,524		—		16,624
	Total		43,112			10,218		—		53,330
	Less: Amounts included in cash and cash
	equivalents		(31,772		)	—		—		(31,772		)
			$	11,340		$	10,218	$	—	$	21,558

Stockbased_Compensation_Tables

Stock-based Compensation (Tables)	9 Months Ended
	Jun. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs	'
	The following table outlines the effects of total stock-based compensation including expense related to SARs.
		Three Months Ended								Nine Months Ended
		June 30,								June 30,
		2014				2013				2014			2013
					(In thousands)
	Stock-based compensation
	Cost of sales	$	50			$	46			$	154		$	133
	Research and development	694				566				2,119			1,665
	Selling, general and administrative	1,017				852				3,156			2,575
	Total stock-based compensation	1,761				1,464				5,429			4,373
	Tax effect on stock-based compensation	(330		)		—				(1,018		)	—
	Net effect on net income	$	1,431			$	1,464			$	4,411		$	4,373
	Compensation related to SARs included in total stock-based compensation	$	222			$	—			$	844		$	—
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	'
	The weighted average estimated fair values of stock option grants and rights granted under the ESPP, as well as the weighted average assumptions used in calculating these values during the three and nine month periods ended June 30, 2014 and 2013 were based on estimates at the date of grant as follows:
		Three Months Ended								Nine Months Ended
		June 30,								June 30,
		2014				2013				2014			2013
	Options
	Weighted-average fair value of grants	$	6.13			$	4.31			$	4.7		$	4.31
	Expected term in years	4.42				4.45				4.42			4.45
	Estimated volatility	51		%		55		%		51		%	59		%
	Risk-free interest rate	1.21		%		0.62		%		1.04		%	0.53		%
	Dividend yield	—		%		—		%		—		%	—		%
	ESPP
	Weighted-average fair value of grants	$	—			$	—			$	2.66		$	2.3
	Expected term in years	—				—				0.49			0.49
	Estimated volatility	—		%		—		%		27		%	32		%
	Risk-free interest rate	—		%		—		%		0.41		%	0.11		%
	Dividend yield	—		%		—		%		—		%	—		%
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding and Exercisable	'
	A summary of the Company’s stock option activity and related information for the nine months ended June 30, 2014 follows (number of shares and aggregate intrinsic value are presented in thousands):
		Number of			Weighted-Average				Weighted-Average		Aggregate
		Shares			Exercise Price				Remaining		Intrinsic Value
									Contractual Term in Years
	Outstanding at September 30, 2013	5,351			$	7.51
	Granted	468			$	11.22
	Exercised	(1,239	)		$	6.77					$	7,632
	Cancelled/Expired	(121	)		$	10.18
	Outstanding at June 30, 2014	4,459			$	8.03			3.94		$	30,036
	Exercisable at June 30, 2014	2,759			$	6.87			3.13		$	21,800
	Vested and expected to vest after June 30, 2014	4,384			$	8			3.91		$	29,689
Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity	'
	A summary of the Company’s RSU activity and related information for the nine months ended June 30, 2014 under the 2007 Plan follows (number of shares and aggregate intrinsic value are presented in thousands):
		Number of			Weighted-Average				Aggregate
		Shares			Grant Date				Intrinsic Value
					Fair Value
	Outstanding at September 30, 2013	269			$	9.02
	Granted	88			$	11.62
	Vested	(92	)		$	8.91			$	1,062
	Forfeited	(1	)		$	10.64
	Outstanding at June 30, 2014	264			$	9.92			$	3,899
Schedule of Share-based Compensation, Stock Appreciation Rights Award Activity	'
	A summary of the Company’s SAR activity and related information for the nine months ended June 30, 2014 under the 2007 Plan follows (number of shares and aggregate intrinsic value are presented in thousands):
		Number of			Weighted-Average				Weighted-Average		Aggregate
		Shares			Exercise Price				Remaining		Intrinsic Value
									Contractual Term in Years
	Outstanding at September 30, 2013	—			$	—
	Granted	779			$	10.96
	Exercised	(3	)		$	10.96
	Cancelled/Expired	(18	)		$	10.96
	Outstanding at June 30, 2014	758			$	10.96			6.32		$	2,889
	Exercisable at June 30, 2014	62			$	10.96			6.28		$	237

Inventories_Tables

Inventories (Tables)	9 Months Ended
	Jun. 30, 2014
Inventory Disclosure [Abstract]	'
Schedule of Inventory, Current	'
	The following is a summary of inventories by major category:
		June 30,		September 30,
		2014		2013
		(In thousands)
	Purchased components	$	18,193	$	14,039
	Work-in-process	27,570		20,960
	Finished goods	34,334		33,470
		$	80,097	$	68,469

Other_Assets_Tables

Other Assets (Tables)	9 Months Ended
	Jun. 30, 2014
Other Assets [Abstract]	'
Schedule of Other Assets	'
	Other assets consisted of the following:
		June 30,		September 30,
		2014		2013
		(In thousands)
	Restricted assets	$	508	$	811
	Other investment	1,469		1,684
	Nanya private placement shares	10,831		10,920
	Technology licenses, net	9,456		2,002
	Other	1,182		1,162
		$	23,446	$	16,579

Purchased_Intangible_Assets_Ta

Purchased Intangible Assets (Tables)	9 Months Ended
	Jun. 30, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Schedule of Finite-Lived Intangible Assets by Major Class	'
	The following tables present details of the Company’s total purchased intangible assets:
			Gross		Accumulated		Net
					Amortization
			(In thousands)
	June 30, 2014
	Developed technology		$	5,330	$	2,414	$	2,916
	Customer relationships		3,340		997		2,343
	Other		450		269		181
	Total		$	9,120	$	3,680	$	5,440
	September 30, 2013
	Developed technology		$	5,330	$	1,758	$	3,572
	Customer relationships		3,340		580		2,760
	Other		450		156		294
	Total		$	9,120	$	2,494	$	6,626
Schedule of amortization expense of purchased intangible assets as reported in the consolidated statements of income	'
	The following table presents details of the amortization expense of purchased intangible assets as reported in the consolidated statements of income:
			Three Months Ended				Nine Months Ended
			June 30,				June 30,
			2014		2013		2014		2013
			(In thousands)
	Reported as:
	Cost of sales		$	191	$	222	$	656	$	647
	Operating expenses		177		176		530		544
	Total		$	368	$	398	$	1,186	$	1,191
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	'
	The following table presents the estimated future amortization expense of the Company’s purchased intangible assets at June 30, 2014 (in thousands). The weighted-average remaining amortization period for developed technology, customer relationships and other intangibles is 4.29 years, 4.21 years and 1.21 years, respectively. If the Company acquires additional purchased intangible assets in the future, its future amortization may be increased by those assets.
	Fiscal year
	Remainder of 2014	$	347
	2015	1,382
	2016	1,238
	2017	1,239
	2018	1,195
	Thereafter	39
	Total	$	5,440

Borrowings_Tables

Borrowings (Tables)	9 Months Ended
	Jun. 30, 2014
Debt Disclosure [Abstract]	'
Schedule of Maturities of Long-term Debt	'
	Principal payments due under the Loan are as follows (in thousands):
	Fiscal year
	Remainder of 2014	$	49
	2015	195
	2016	195
	2017	195
	2018	195
	Thereafter	3,754
	Total	$	4,583

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Tables)	9 Months Ended
	Jun. 30, 2014
Stockholders' Equity Note [Abstract]	'
Schedule of Accumulated Other Comprehensive Income (Loss)	'
	The components of accumulated other comprehensive income, net of tax, were as follows:
		June 30,			September 30,
		2014			2013
		(In thousands)
	Accumulated foreign currency translation adjustments	$	3,767		$	4,787
	Accumulated net unrealized gain on SMIC (net of tax of $0 and $275, respectively)	—			419
	Accumulated net unrealized gain on Nanya (net of tax of $0 and $3,565, respectively)	—			5,959
	Accumulated net retirement plan transition asset (net of tax of $148 and $148, respectively)	2			47
	Accumulated net retirement plan actuarial losses (net of tax of $470 and $470, respectively)	(2,009		)	(2,091		)
	Total accumulated other comprehensive income	$	1,760		$	9,121
Reclassification out of Accumulated Other Comprehensive Income	'
	The significant amounts reclassified out of accumulated other comprehensive income into the consolidated condensed statements of income, with presentation location, during the three and nine months ended June 30, 2014 and June 30, 2013 were as follows:
		Three Months Ended						Nine Months Ended
		June 30,						June 30,
		2014			2013			2014			2013
		(In thousands)
	Comprehensive Income Components	Amount Reclassified from Accumulated Other Comprehensive Income						Amount Reclassified from Accumulated Other Comprehensive Income						Location
	Unrealized holding gains (losses) on available-for -sale investments
		$	1,616		$	4,428		$	9,618		$	5,232		Gain on the sale of investments
		(592		)	(2,057		)	(3,589		)	(2,193		)	Provision for income taxes
		$	1,024		$	2,371		$	6,029		$	3,039

Per_Share_Data_Tables

Per Share Data (Tables)	9 Months Ended
	Jun. 30, 2014
Earnings Per Share [Abstract]	'
Schedule of Earnings Per Share, Basic and Diluted	'
	The following table sets forth the computation of basic and diluted net income per share (in thousands, except per share amounts):
		Three Months Ended				Nine Months Ended
		June 30,				June 30,
		2014		2013		2014		2013
	Numerator for basic and diluted net income per share:
	Net income attributable to ISSI	$	6,186	$	7,064	$	20,433	$	12,850
	Denominator for basic net income per share:
	Weighted average common shares outstanding	30,312		28,293		29,816		27,988
	Dilutive stock options and awards	1,651		1,462		1,521		1,439
	Denominator for diluted net income per share	31,963		29,755		31,337		29,427
	Basic net income per share	$	0.2	$	0.25	$	0.69	$	0.46
	Diluted net income per share	$	0.19	$	0.24	$	0.65	$	0.44

Geographic_and_Segment_Informa1

Geographic and Segment Information (Tables)	9 Months Ended
	Jun. 30, 2014
Segment Reporting [Abstract]	'
Schedule of Revenue from External Customers Attributed to Foreign Countries by Geographic Area	'
	The following table summarizes the Company’s operations in different geographic areas:
		Three Months Ended				Nine Months Ended
		June 30,				June 30,
		2014		2013		2014		2013
				(In thousands)
	Net sales
	United States	$	9,571	$	9,517	$	28,449	$	27,731
	China	9,838		10,477		32,689		20,579
	Hong Kong	16,456		13,638		45,499		50,532
	Japan	5,916		8,194		16,569		23,241
	Korea	4,000		3,311		10,544		10,064
	Taiwan	12,344		11,230		35,099		30,447
	Other Asia Pacific countries	6,435		5,880		18,390		18,374
	Europe	19,587		14,797		56,207		46,681
	Other	687		744		1,379		1,529
	Total net sales	$	84,834	$	77,788	$	244,825	$	229,178
Schedule of Disclosure on Geographic Areas, Long-Lived Assets in Individual Foreign Countries by Country	'
		June 30,		September 30,
		2014		2013
		(In thousands)
	Long-lived assets
	United States	$	10,943	$	9,696
	Hong Kong	16		7
	China	3,955		3,424
	Taiwan	35,307		33,377
		$	50,221	$	46,504

Basis_of_Presentation_Basis_of

Basis of Presentation Basis of Presentation (Details) (USD $)	9 Months Ended		1 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Oct. 31, 2013	31-May-13	Jun. 30, 2014	Sep. 14, 2012
			Chingis Technology Corporation	Chingis Technology Corporation	Chingis Technology Corporation	Chingis Technology Corporation
Business Acquisition [Line Items]	'	'	'	'	'	'
Percentage of interests acquired	'	'	'	'	'	94.10%
Percentage of additional voting interests acquired	'	'	0.50%	4.80%	'	'
Additional interest acquired	$199	$1,614	$200	$1,600	'	'
Percentage ownership of Chingis	'	'	'	'	99.40%	'

Fair_Value_Measurements_Narrat

Fair Value Measurements (Narrative) (Details) (USD $)	Jun. 30, 2014	Sep. 30, 2013	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2014
In Millions, unless otherwise specified	Foreign	Foreign	China	Nanya Technology Corporation	Nanya Technology Corporation	Semiconductor Manufacturing International Corp.
Segment Reporting Information [Line Items]	'	'	'	'	'	'
Shares sold of Nanya common stock	'	'	'	23.2	109.6	29.9
Proceeds from sale of Nanya common stock	'	'	'	$3.60	$16.20	$3.20
Pre-tax gain on sale of Nanya common stock	'	'	'	2.1	9.2	2.1
Cash and cash equivalents, and short-term investments	$70.20	$71.20	$2	'	'	'

Fair_Value_Measurements_Assets

Fair Value Measurements (Assets and Liabilities that are Measured at Fair Value on a Recurring Basis) (Details) (USD $)	Jun. 30, 2014		Sep. 30, 2013
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Fair Value	$40,587		$53,330
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Fair Value	19,321		37,735
Money market instruments	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Fair Value	19,321		19,318
Money market instruments | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Fair Value	19,321	[1]	19,318	[1]
Available-for-sale Securities | Semiconductor Manufacturing International Corp.	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Fair Value	'		1,793
Available-for-sale Securities | Semiconductor Manufacturing International Corp. | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Fair Value	0	[2]	1,793	[2]
Available-for-sale Securities | Nanya Technology Corporation	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Fair Value	0		16,624
Available-for-sale Securities | Nanya Technology Corporation | Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Fair Value	$0	[2]	$16,624	[2]
[1]	Included in cash and cash equivalents
[2]	Included in short-term investments

Fair_Value_Measurements_Market

Fair Value Measurements (Marketable Equity and Cash Equivalents (Classified as Available-for-sale) and Cost Method Investments) (Details) (USD $)	9 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Sep. 30, 2013
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	$40,587	$43,112
Gross Unrealized Holding Gains	0	10,218
Gross Unrealized Holding Losses	0	0
Fair Value	40,587	53,330
Money market instruments	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	19,321	19,318
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Fair Value	19,321	19,318
Certificates of deposit	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	21,266	15,595
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Fair Value	21,266	15,595
Cash and Cash Equivalents	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	38,841	31,772
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Fair Value	38,841	31,772
Short-term Investments	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	1,746	11,340
Gross Unrealized Holding Gains	0	10,218
Gross Unrealized Holding Losses	0	0
Fair Value	1,746	21,558
Semiconductor Manufacturing International Corp. | Available-for-sale Securities	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	'	1,099
Gross Unrealized Holding Gains	'	694
Gross Unrealized Holding Losses	'	0
Fair Value	'	1,793
Nanya Technology Corporation | Available-for-sale Securities	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	0	7,100
Gross Unrealized Holding Gains	0	9,524
Gross Unrealized Holding Losses	0	0
Fair Value	$0	$16,624

Stockbased_Compensation_Narrat

Stock-based Compensation (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Shares available for future grant under the 2007 Plan (shares)	1,811,000	'	1,811,000	'
Option vesting period (years)	'	'	'4 years	'
Percentage discount from fair market value for shares purchased under the Employee Stock Purchase Plan	'	'	85.00%	'
Offering period (years)	'6 months	'	'	'
Shares available for future issuance under the Employee Stock Purchase Plan (shares)	453,000	'	453,000	'
Prior to October 1 2005	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Option expiration period (years)	'	'	'10 years	'
After October 1 2005	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Option expiration period (years)	'	'	'7 years	'
Minimum	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Option Cliff vesting period	'	'	'6 months	'
Maximum	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Option Cliff vesting period	'	'	'1 year	'
Restricted Stock Units (RSUs)	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Weighted-average fair value of grants	$14.45	'	$11.62	$9.14
Restricted Stock Units (RSUs) | Minimum	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
RSU vesting period (years)	'	'	'2 years	'
Restricted Stock Units (RSUs) | Maximum	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
RSU vesting period (years)	'	'	'4 years	'
SARS	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Option vesting period (years)	'	'	'4 years	'
Option expiration period (years)	'	'	'7 years	'
Total unrecognized stock-based compensation expense	$4,400	'	$4,400	'
Nonvested awards, total compensation cost not yet recognized, period for recognition (years)	'	'	'3 years 4 months 10 days	'
SARS | Minimum	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Option Cliff vesting period	'	'	'6 months	'
SARS | Maximum	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Option Cliff vesting period	'	'	'1 year	'
Options	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Total unrecognized stock-based compensation expense	9,400	'	9,400	'
Nonvested awards, total compensation cost not yet recognized, period for recognition (years)	'	'	'2 years 2 months 23 days	'
ESPP	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Total unrecognized stock-based compensation expense	$54	'	$54	'
Nonvested awards, total compensation cost not yet recognized, period for recognition (years)	'	'	'1 month	'
Weighted-average fair value of grants	$0	$0	$2.66	$2.30

Stockbased_Compensation_Schedu

Stock-based Compensation (Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Allocated share-based compensation expense	$1,761	$1,464	$5,429	$4,373
Tax effect on stock-based compensation	-330	0	-1,018	0
Net effect on net income	1,431	1,464	4,411	4,373
SARS	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Net effect on net income	222	0	844	0
Cost of sales	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Allocated share-based compensation expense	50	46	154	133
Research and development	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Allocated share-based compensation expense	694	566	2,119	1,665
Selling, general and administrative	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Allocated share-based compensation expense	$1,017	$852	$3,156	$2,575

Stockbased_Compensation_Shareb

Stock-based Compensation (Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value) (Details) (USD $)	3 Months Ended		9 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Options	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Weighted-average fair value of grants	$6.13	$4.31	$4.70	$4.31
Expected term in years	'4 years 5 months 1 day	'4 years 5 months 12 days	'4 years 5 months 1 day	'4 years 5 months 12 days
Estimated volatility	51.00%	55.00%	51.00%	59.00%
Risk-free interest rate	1.21%	0.62%	1.04%	0.53%
Dividend yield	0.00%	0.00%	0.00%	0.00%
ESPP	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Weighted-average fair value of grants	$0	$0	$2.66	$2.30
Expected term in years	'	'	'5 months 27 days	'5 months 27 days
Estimated volatility	0.00%	0.00%	27.00%	32.00%
Risk-free interest rate	0.00%	0.00%	0.41%	0.11%
Dividend yield	0.00%	0.00%	0.00%	0.00%

Stockbased_Compensation_Shareb1

Stock-based Compensation (Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding and Exercisable) (Details) (Options, USD $)	9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014
Options	'
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]	'
Outstanding at September 30, 2013	5,351
Granted	468
Exercised	-1,239
Cancelled/Expired	-121
Outstanding at June 30, 2014	4,459
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]	'
Outstanding at September 30, 2013	$7.51
Granted	$11.22
Exercised	$6.77
Cancelled/Expired	$10.18
Outstanding at June 30, 2014	$8.03
Aggregate Intrinsic Value, options exercised	$7,632
Weighted-Average Remaining Contractual Term in Years, Outstanding at June 30, 2014 (years)	'3 years 11 months 9 days
Aggregate Intrinsic Value, Outstanding at June 30, 2014	30,036
Number of Shares, Exercisable at June 30, 2014 (shares)	2,759
Weighted-Average Exercise Price, Exercisable at June 30, 2014	$6.87
Weighted-Average Remaining Contractual Term in Years, Exercisable at June 30, 2014 (years)	'3 years 1 month 17 days
Aggregate Intrinsic Value, Exercisable at June 30, 2014	21,800
Number of Shares, Vested and expected to vest after June 30, 2014 (shares)	4,384
Weighted-Average Exercise Price, Vested and expected to vest after June 30, 2014	$8
Weighted-Average Remaining Contractual Term in Years, Vested and expected to vest after June 30, 2014 (years)	'3 years 10 months 28 days
Aggregate Intrinsic Value, Vested and expected to vest after June 30, 2014	$29,689

Stockbased_Compensation_Restri

Stock-based Compensation (Restricted Stock and Restricted Stock Units Activity) (Details) (Restricted Stock Units (RSUs), USD $)	3 Months Ended	9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2013
Restricted Stock Units (RSUs)	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]	'	'	'
Outstanding at September 30, 2013	'	269	'
Granted	'	88	'
Vested	'	-92	'
Forfeited	'	-1	'
Outstanding at June 30, 2014	264	264	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]	'	'	'
Outstanding at September 30, 2012, Weighted-Average Grant Date Fair Value	'	$9.02	'
Weighted-average fair value of grants	$14.45	$11.62	$9.14
Weighted average grant date fair value, vested	'	$8.91	'
Weighted average grant date fair value, forfeited	'	$10.64	'
Outstanding at June 30, 2014, Weighted-Average Grant Date Fair Value	$9.92	$9.92	'
Aggregate Intrinsic Value, Vested	'	$1,062,000	'
Aggregate Intrinsic Value, Outstanding at June 30, 2014	$3,899,000	$3,899,000	'

Stockbased_Compensation_Schedu1

Stock-based Compensation (Schedule of SAR Activity) (Details) (SARS, USD $)	9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014
SARS	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]	'
Outstanding at September 30, 2013	0
Granted	779
Exercised	-3
Cancelled/Expired	-18
Outstanding at June 30, 2014	758
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]	'
Outstanding at September 30, 2013	$0
Granted	$10.96
Exercised	$10.96
Cancelled/Expired	$10.96
Outstanding at June 30, 2014	$10.96
Weighted-Average Remaining Contractual Term in Years, Outstanding at June 30, 2014 (years)	'6 years 3 months 26 days
Aggregate Intrinsic Value, Outstanding at June 30, 2014	$2,889
Number of Shares, Exercisable at June 30, 2014 (shares)	62
Weighted-Average Exercise Price, Exercisable at June 30, 2014	$10.96
Weighted-Average Remaining Contractual Term in Years, Exercisable at June 30, 2014 (years)	'6 years 3 months 11 days
Aggregate Intrinsic Value, Exercisable at June 30, 2014	$237

Concentrations_Narrative_Detai

Concentrations (Narrative) (Details) (Sales Revenue, Goods, Net)	3 Months Ended		9 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Largest Distributor	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Concentration Risk, Largest Customers	20.00%	13.00%	18.00%	14.00%
Second Largest Distributor	'	'	'	'
Concentration Risk [Line Items]	'	'	'	'
Concentration Risk, Largest Customers	12.00%	10.00%	13.00%	11.00%

Inventories_Narrative_Details

Inventories (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Inventory Disclosure [Abstract]	'	'	'	'
Inventory Write-down	$2.10	$1.20	$4.30	$3.50

Inventories_Schedule_of_Invent

Inventories (Schedule of Inventory, Current by major category) (Details) (USD $)	Jun. 30, 2014	Sep. 30, 2013
In Thousands, unless otherwise specified
Inventory Disclosure [Abstract]	'	'
Purchased components	$18,193	$14,039
Work-in-process	27,570	20,960
Finished goods	34,334	33,470
Inventories	$80,097	$68,469	[1]
[1]	Derived from audited financial statements.

Other_Assets_Narrative_Details

Other Assets (Narrative) (Details) (USD $)	1 Months Ended				9 Months Ended
	Sep. 30, 2012	Jun. 30, 2014	Sep. 30, 2013	Mar. 31, 2012	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2014	Jun. 30, 2014
					Technology licenses, net	Technology licenses, net	Hong Kong	Pledged Nanya private placement shares
					Minimum	Maximum
Entity Information [Line Items]	'	'	'	'	'	'	'	'
Purchases of available for sale securities	$27,100,000	'	'	'	'	'	'	'
Termination period	'1 year	'	'	'	'	'	'	'
Nanya private placement shares	'	10,831,000	10,920,000	'	'	'	'	5,300,000
Estimated useful lives	'	'	'	'	'3 years	'10 years	'	'
Other investment	'	$1,469,000	$1,684,000	$2,000,000	'	'	'	'
Equity method investment ownership percentage	'	'	'	'	'	'	31.00%	'

Other_Assets_Schedule_of_Other

Other Assets (Schedule of Other Assets) (Details) (USD $)	Jun. 30, 2014	Sep. 30, 2013		Mar. 31, 2012
In Thousands, unless otherwise specified
Finite-Lived Intangible Assets [Line Items]	'	'		'
Restricted assets	$508	$811		'
Other investment	1,469	1,684		2,000
Nanya private placement shares	10,831	10,920		'
Other	1,182	1,162		'
Other assets	23,446	16,579	[1]	'
Technology licenses, net	'	'		'
Finite-Lived Intangible Assets [Line Items]	'	'		'
Technology licenses, net	$9,456	$2,002		'
[1]	Derived from audited financial statements.

Purchased_Intangible_Assets_Na

Purchased Intangible Assets (Narrative) (Details)	9 Months Ended
	Jun. 30, 2014
Developed technology	'
Acquired Indefinite-lived Intangible Assets [Line Items]	'
Weighted average useful life for intangibles (years)	'4 years 3 months 15 days
Customer relationships	'
Acquired Indefinite-lived Intangible Assets [Line Items]	'
Weighted average useful life for intangibles (years)	'4 years 2 months 16 days
Other	'
Acquired Indefinite-lived Intangible Assets [Line Items]	'
Weighted average useful life for intangibles (years)	'1 year 2 months 16 days

Purchased_Intangible_Assets_Sc

Purchased Intangible Assets (Schedule of Finite-Lived Intangible Assets by Major Class) (Details) (USD $)	Jun. 30, 2014	Sep. 30, 2013
In Thousands, unless otherwise specified
Finite-Lived Intangible Assets [Line Items]	'	'
Gross	$9,120	$9,120
Accumulated Amortization	3,680	2,494
Net	5,440	'
Total, Net	5,440	6,626	[1]
Developed technology	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Gross	5,330	5,330
Accumulated Amortization	2,414	1,758
Net	2,916	3,572
Customer relationships	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Gross	3,340	3,340
Accumulated Amortization	997	580
Net	2,343	2,760
Other	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Gross	450	450
Accumulated Amortization	269	156
Net	$181	$294
[1]	Derived from audited financial statements.

Purchased_Intangible_Assets_Sc1

Purchased Intangible Assets (Schedule of Current Finite-Lived Intangible Asset Amortization Expense by Income Statement Line Item) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Schedule of Current Intangible Asset Amortization Expense By Income Statement Line Item [Line Items]	'	'	'	'
Amortization of intangibles	$368	$398	$1,186	$1,191
Cost of sales	'	'	'	'
Schedule of Current Intangible Asset Amortization Expense By Income Statement Line Item [Line Items]	'	'	'	'
Amortization of intangibles	191	222	656	647
Operating expenses	'	'	'	'
Schedule of Current Intangible Asset Amortization Expense By Income Statement Line Item [Line Items]	'	'	'	'
Amortization of intangibles	$177	$176	$530	$544

Purchased_Intangible_Assets_Sc2

Purchased Intangible Assets (Schedule Finite-Lived Intangible Assets, Future Amortization Expense) (Details) (USD $)	Jun. 30, 2014
In Thousands, unless otherwise specified
Goodwill and Intangible Assets Disclosure [Abstract]	'
Remainder of 2014	$347
2015	1,382
2016	1,238
2017	1,239
2018	1,195
Thereafter	39
Net	$5,440

Borrowings_Narrative_Details

Borrowings (Narrative) (Details) (USD $)	9 Months Ended		1 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2012
			Secured Debt	Secured Debt
			sqft	LIBOR
			acre
Debt Instrument [Line Items]	'	'	'	'
Proceeds from borrowings	$0	$4,875,000	$4,900,000	'
Purchase price of headquarters	'	'	$6,500,000	'
Acres of land	'	'	2.85	'
Square footage of building	'	'	55,612	'
Interest rate spread above LIBOR	'	'	'	1.00%
LIBOR	'	'	'	'LIBOR

Borrowings_Schedule_of_Maturit

Borrowings (Schedule of Maturities of Debt) (Details) (USD $)	Jun. 30, 2014
In Thousands, unless otherwise specified
Debt Disclosure [Abstract]	'
Remainder of 2014	$49
2015	195
2016	195
2017	195
2018	195
Thereafter	3,754
Total	$4,583

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $)	Jun. 30, 2014	Sep. 30, 2013
In Thousands, unless otherwise specified
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'
Accumulated foreign currency translation adjustments	$3,767	$4,787
Accumulated net retirement plan transition asset (net of tax of $148 and $148, respectively)	2	47
Accumulated net retirement plan actuarial losses (net of tax of $470 and $470, respectively)	-2,009	-2,091
Total accumulated other comprehensive income	1,760	9,121	[1]
Accumulated net retirement plan transition asset, tax	148	148
Accumulated net retirement plan actuarial losses, tax	470	470
Semiconductor Manufacturing International Corp.	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'
Accumulated net unrealized gain	0	419
Accumulated unrealized gain, tax	0	275
Nanya Technology Corporation	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'
Accumulated net unrealized gain	0	5,959
Accumulated unrealized gain, tax	$0	$3,565
[1]	Derived from audited financial statements.

Accumulated_Other_Comprehensiv3

Accumulated Other Comprehensive Income (Schedule of Reclassification out of Accumulated Other Comprehensive Income) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Reclassification out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Gain on sale of investments	$2,140	$7,280	$11,300	$9,339
Provision for income taxes	-2,388	-5,215	-6,941	-9,619
Consolidated net income	6,227	7,246	20,631	13,014
Amount Reclassified from Accumulated Other Comprehensive Income | Unrealized Holding Gains (Losses) on Available-for-Sale Investments	'	'	'	'
Reclassification out of Accumulated Other Comprehensive Income [Line Items]	'	'	'	'
Gain on sale of investments	1,616	4,428	9,618	5,232
Provision for income taxes	-592	-2,057	-3,589	-2,193
Consolidated net income	$1,024	$2,371	$6,029	$3,039

Income_Taxes_Narrative_Details

Income Taxes (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Operating Loss Carryforwards [Line Items]	'	'	'	'
Income tax expense	$2,388,000	$5,215,000	$6,941,000	$9,619,000
Effective tax rate	28.00%	42.00%	25.00%	42.00%
Federal statutory rate	'	'	35.00%	35.00%
Foreign Tax Credit Carryforward	'	'	'	'
Operating Loss Carryforwards [Line Items]	'	'	'	'
Increase in valuation allowance	'	-1,300,000	'	-1,300,000
Research Tax Credit Carryforward	'	'	'	'
Operating Loss Carryforwards [Line Items]	'	'	'	'
Increase in valuation allowance	'	500,000	'	500,000
Valuation Allowance, Operating Loss Carryforwards	'	'	'	'
Operating Loss Carryforwards [Line Items]	'	'	'	'
Increase in valuation allowance	'	'	'	$1,500,000

Per_Share_Data_Narrative_Detai

Per Share Data (Narrative) (Details)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share [Abstract]	'	'	'	'
Stock options and awards excluded from diluted earnings per share (shares)	686	2,864	1,070	2,849

Per_Share_Data_Calculation_of_

Per Share Data (Calculation of Basic and Diluted EPS) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share [Abstract]	'	'	'	'
Net income attributable to ISSI	$6,186	$7,064	$20,433	$12,850
Denominator for basic net income per share:	'	'	'	'
Weighted average common shares outstanding	30,312	28,293	29,816	27,988
Dilutive stock options and awards	1,651	1,462	1,521	1,439
Denominator for diluted net income per share	31,963	29,755	31,337	29,427
Basic net income per share (in dollars per share)	$0.20	$0.25	$0.69	$0.46
Diluted net income per share (in dollars per share)	$0.19	$0.24	$0.65	$0.44

Common_Stock_Repurchase_Progra1

Common Stock Repurchase Program (Narrative) (Details) (USD $)	9 Months Ended	82 Months Ended
In Millions, except Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2014
Common Stock Repurchase Program [Abstract]	'	'
Stock repurchased and retired during period (shares)	'	14,179,711
Stock repurchased and retired during period, value	'	$88.50
Stock repurchase program, remaining authorized repurchase amount	19.8	'
Shares paid for tax withholding for share based compensation (shares)	30,323	'
Payments related to tax withholding for share-based compensation	$0.40	'

Commitments_and_Contingencies_

Commitments and Contingencies (Narrative) (Details) (USD $)	Jun. 30, 2014
In Millions, unless otherwise specified
Commitments and Contingencies Disclosure [Abstract]	'
Amount of purchase orders that had been entered into wafer work-in-process	$26.60

Geographic_and_Segment_Informa2

Geographic and Segment Information (Schedule of Revenues, by Geographical Areas) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Net sales	$84,834	$77,788	$244,825	$229,178
United States	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Net sales	9,571	9,517	28,449	27,731
China	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Net sales	9,838	10,477	32,689	20,579
Hong Kong	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Net sales	16,456	13,638	45,499	50,532
Japan	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Net sales	5,916	8,194	16,569	23,241
Korea	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Net sales	4,000	3,311	10,544	10,064
Taiwan	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Net sales	12,344	11,230	35,099	30,447
Other Asia Pacific countries	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Net sales	6,435	5,880	18,390	18,374
Europe	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Net sales	19,587	14,797	56,207	46,681
Other	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Net sales	$687	$744	$1,379	$1,529

Geographic_and_Segment_Informa3

Geographic and Segment Information (Schedule of Long-Lived Assets, by Geographical Areas) (Details) (USD $)	Jun. 30, 2014	Sep. 30, 2013
In Thousands, unless otherwise specified
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'
Long-lived assets	$50,221	$46,504
United States	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'
Long-lived assets	10,943	9,696
Hong Kong	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'
Long-lived assets	16	7
China	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'
Long-lived assets	3,955	3,424
Taiwan	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'
Long-lived assets	$35,307	$33,377

Related_Party_Transactions_Nar

Related Party Transactions (Narrative) (Details) (Jimmy S.M. Lee, Executive Chairman, USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Sep. 30, 2013
Jimmy S.M. Lee, Executive Chairman	'	'	'	'	'
Related Party Transaction [Line Items]	'	'	'	'	'
Revenue from related parties	$80	$104	$162	$294	'
Accounts receivable, related parties	$26	'	$26	'	$65