Note 8 - Convertible Debt (Details Textual) - Convertible Debt [Member] $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2016 USD ($) $ / shares $ / item	Dec. 31, 2015 USD ($) $ / shares $ / item
Convertible Notes 2015 [Member]
Debt Instrument, Face Amount		$ 230,000
Debt Instrument, Interest Rate, Stated Percentage		1.125%
Debt Instrument, Convertible, Conversion Ratio		24.8988
Debt Instrument, Convertible, Conversion Price \| $ / shares		$ 40.16
Capped Call, Aggregate Call Options Purchased, Percentage Related to Shares Underlying the Convertible Note		100.00%
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger		98.00%
Convertible Debt Holders in Default, Percent of Principal Amount		25.00%
Convertible Debt in Default, Percent Holders to Declare Due and Payable		100.00%
Convertible Debt in Bankruptcy, Insolvency, and Reorganization, Percent due and Payable		100.00%
Proceeds from Convertible Debt		$ 230,000
Convertible Debt, Total		175,974
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt		54,026
Debt Issuance Costs, Gross		6,359
Payments of Debt Issuance Costs		6,007
Unamortized Debt Issuance Expense		4,864
Debt Instrument, Convertible Equity Component Issuance Cost		$ 1,495
Derivative, Cap Price \| $ / item		52.06
Payments for Call Options		$ 17,802
Convertible Notes 2015 [Member] \| Conversion Circumstance 1 [Member]
Debt Instrument, Convertible, Threshold Trading Days		20
Debt Instrument, Convertible, Threshold Consecutive Trading Days		30
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger		130.00%
Convertible Notes 2015 [Member] \| Conversion Circumstance 2 [Member]
Debt Instrument, Convertible, Threshold Trading Days		5
Debt Instrument, Convertible, Threshold Consecutive Trading Days		5
Convertible Notes 2016 [Member]
Debt Instrument, Face Amount	$ 287,500
Debt Instrument, Interest Rate, Stated Percentage	0.75%
Debt Instrument, Convertible, Conversion Ratio	17.7508
Debt Instrument, Convertible, Conversion Price \| $ / shares	$ 56.34
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger	98.00%
Convertible Debt Holders in Default, Percent of Principal Amount	25.00%
Convertible Debt in Default, Percent Holders to Declare Due and Payable	100.00%
Convertible Debt in Bankruptcy, Insolvency, and Reorganization, Percent due and Payable	100.00%
Proceeds from Convertible Debt	$ 287,500
Convertible Debt, Total	216,775
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt	70,725
Debt Issuance Costs, Gross	5,798
Debt Instrument, Convertible Equity Component Issuance Cost	$ 1,891
Derivative, Cap Price \| $ / item	73.03
Payments for Call Options	$ 22,540
Debt Instrument, Repurchase Price, Percentage of Principal Amount Repurchased	100.00%
Debt and Equity Issuance Costs, Net	$ 7,689
Convertible Notes 2016 [Member] \| Conversion Circumstance 1 [Member]
Debt Instrument, Convertible, Threshold Trading Days	20
Debt Instrument, Convertible, Threshold Consecutive Trading Days	30
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger	130.00%
Convertible Notes 2016 [Member] \| Conversion Circumstance 2 [Member]
Debt Instrument, Convertible, Threshold Trading Days	5
Debt Instrument, Convertible, Threshold Consecutive Trading Days	5

The total number of shares outstanding, in terms of percentage, that were purchased under a Capped Call.

No definition available.

Name:	iphi_CappedCallAggregateCallOptionsPurchasedPercentageRelatedToSharesUnderlyingTheConvertibleNote
Namespace Prefix:	iphi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage of convertible notes held by an individual compared to the total convertible notes outstanding.

+ References

No definition available.

+ Details

Name:	iphi_ConvertibleDebtHoldersInDefaultPercentOfPrincipalAmount
Namespace Prefix:	iphi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The payable percentage of the convertible note due to holders at the event of bankruptcy, insolvency, reorganization.

+ References

No definition available.

+ Details

Name:	iphi_ConvertibleDebtInBankruptcyInsolvencyAndReorganizationPercentDueAndPayable
Namespace Prefix:	iphi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The payable percentage due at the event of a company default (other than bankruptcy, insolvency, or reorganization).

+ References

No definition available.

+ Details

Name:	iphi_ConvertibleDebtInDefaultPercentHoldersToDeclareDueAndPayable
Namespace Prefix:	iphi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount, after accumulated amortization, of debt and equity issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

No definition available.

+ Details

Name:	iphi_DebtAndEquityIssuanceCostsNet
Namespace Prefix:	iphi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The issuance costs associated with the convertible equity component of a debt instrument.

+ References

No definition available.

+ Details

Name:	iphi_DebtInstrumentConvertibleEquityComponentIssuanceCost
Namespace Prefix:	iphi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of principal amount of debt repurchased.

+ References

No definition available.

+ Details

Name:	iphi_DebtInstrumentRepurchasePricePercentageOfPrincipalAmountRepurchased
Namespace Prefix:	iphi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow from the acquisition of call options.

+ References

No definition available.

+ Details

Name:	iphi_PaymentsForCallOptions
Namespace Prefix:	iphi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Adjustment to additional paid in capital resulting from the recognition of convertible debt instruments as two separate components - a debt component and an equity component. This bifurcation may result in a basis difference associated with the liability component that represents a temporary difference for purposes of applying accounting for income taxes. The initial recognition of deferred taxes for the tax effect of that temporary difference is as an adjustment to additional paid in capital.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 25
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=51819886&loc=SL6014347-161799

+ Details

Name:	us-gaap_AdjustmentsToAdditionalPaidInCapitalEquityComponentOfConvertibleDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Including the current and noncurrent portions, carrying amount of debt identified as being convertible into another form of financial instrument (typically the entity's common stock) as of the balance sheet date, which originally required full repayment more than twelve months after issuance or greater than the normal operating cycle of the company.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_ConvertibleDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The price per share of the conversion feature embedded in the debt instrument.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031898-161870

+ Details

Name:	us-gaap_DebtInstrumentConvertibleConversionPrice1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(5))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

Name:	us-gaap_DebtInstrumentConvertibleConversionRatio1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Threshold period of specified consecutive trading days within which common stock price to conversion price of convertible debt instrument must exceed threshold percentage for specified number of trading days to trigger conversion feature.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum percentage of common stock price to conversion price of convertible debt instruments to determine eligibility of conversion.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Threshold number of specified trading days that common stock price to conversion price of convertible debt instruments must exceed threshold percentage within a specified consecutive trading period to trigger conversion feature.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentConvertibleThresholdTradingDays
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28555-108399

+ Details

Name:	us-gaap_DeferredFinanceCostsGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The cap rate on a price risk derivative such as a cap or collar. A payment or receipt is triggered if the market rate exceeds the cap rate on the contract.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeCapPrice
Namespace Prefix:	us-gaap_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585

+ Details

Name:	us-gaap_PaymentsOfDebtIssuanceCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow from the issuance of a long-term debt instrument which can be exchanged for a specified amount of another security, typically the entity's common stock, at the option of the issuer or the holder.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromConvertibleDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_UnamortizedDebtIssuanceExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_ConvertibleDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=iphi_ConvertibleNotes2015Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtConversionByUniqueDescriptionAxis=iphi_ConversionCircumstance1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtConversionByUniqueDescriptionAxis=iphi_ConversionCircumstance2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=iphi_ConvertibleNotes2016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: