Cash And Cash Equivalents And Marketable Securities

No definition available.

Name:	iac_CashAndCashEquivalentsAndMarketableSecurities
Namespace Prefix:	iac_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Debt Instrument, Covenant Terms, Interest Coverage Ratio

+ References

No definition available.

+ Details

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Namespace Prefix:	iac_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Covenant Terms, Leverage Ratio

+ References

No definition available.

+ Details

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Namespace Prefix:	iac_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Covenant Terms, Leverage Ratio Limiting Ability to Pay Dividends, Make Distributions, or Repurchase Stock

+ References

No definition available.

+ Details

Name:	iac_DebtInstrumentCovenantTermsLeverageRatioLimitingAbilitytoPayDividendsMakeDistributionsorRepurchaseStock
Namespace Prefix:	iac_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Percentage of Exchange Price on Applicable Trading day

+ References

No definition available.

+ Details

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Namespace Prefix:	iac_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Percentage of Product of Last Reported Price

+ References

No definition available.

+ Details

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Namespace Prefix:	iac_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Period of Consecutive Reported Sale Price of Common Stock

+ References

No definition available.

+ Details

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Namespace Prefix:	iac_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Period of Reported Sale Price of Common Stock

+ References

No definition available.

+ Details

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Namespace Prefix:	iac_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Redemption, Premium

+ References

No definition available.

+ Details

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Namespace Prefix:	iac_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Long-term Debt, Maturities, Quarterly Repayments of Principal

+ References

No definition available.

+ Details

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Namespace Prefix:	iac_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Long-term Debt, Maturities, Repayments of Principal, Final Payment

+ References

No definition available.

+ Details

Name:	iac_LongtermDebtMaturitiesRepaymentsofPrincipalFinalPayment
Namespace Prefix:	iac_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
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-Section S99
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-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

The amount by which the convertible debt's if-converted value exceeds its principle amount at the balance sheet date, regardless of whether the instrument is currently convertible. This element applies to public companies only.

+ 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 (c)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031898-161870

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

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

+ References

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-Name Accounting Standards Codification
-Topic 835
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-SubTopic 30
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-Paragraph 8
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+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Increase for accrued, but unpaid interest on the debt instrument for the period.

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-Name Accounting Standards Codification
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-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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Balance Type:	credit
Period Type:	duration

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
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-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Balance Type:	na
Period Type:	instant

- Definition

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

+ References

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
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Balance Type:	na
Period Type:	duration

- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph e
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt discount (premium).

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Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
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-Section S99
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Balance Type:	credit
Period Type:	instant

- Definition

The cash inflow from additional borrowings, net of cash paid to third parties in connection with debt origination.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-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

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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Name:	srt_ConsolidatedEntitiesAxis=srt_ParentCompanyMember
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- Details

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- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
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Name:	srt_RangeAxis=srt_MaximumMember
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- Details

Name:	dei_LegalEntityAxis=iac_MatchGroupMember
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Name:	us-gaap_DebtInstrumentAxis=iac_MatchGroupCreditFacilityDueDecember72023Member
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LONG-TERM DEBT - Narrative (Details)						9 Months Ended	12 Months Ended			31 Months Ended
LONG-TERM DEBT - Narrative (Details)	Aug. 23, 2019 USD ($)	May 21, 2019 USD ($)	Dec. 31, 2018 USD ($)	Nov. 05, 2018 USD ($)	Oct. 02, 2017 USD ($)	Sep. 30, 2019 USD ($)	Nov. 05, 2023 USD ($)	Nov. 05, 2022 USD ($)	Dec. 31, 2018 USD ($)	Nov. 05, 2021 USD ($)	Jun. 03, 2019 USD ($)	Feb. 15, 2019 USD ($)	Dec. 04, 2017	Jun. 01, 2016
Debt Instrument [Line Items]
Outstanding balance of debt instrument						$ 3,543,438,000
Net unamortized discount (premium)						(368,976,000)
Cash And Cash Equivalents And Marketable Securities						2,300,000,000
IAC
Debt Instrument [Line Items]
Net unamortized discount (premium)			$ 54,025,000			362,390,000			$ 54,025,000
Debt redeemed			551,989,000			1,667,500,000			551,989,000
IAC Credit Facility \| Revolving Credit Facility
Debt Instrument [Line Items]
Borrowings outstanding of credit facility			$ 0			$ 0			$ 0
Annual commitment fee on undrawn funds, basis points (as a percent)						0.20%			0.20%
Maximum borrowing capacity						$ 250,000,000
IAC Credit Facility \| Maximum \| Revolving Credit Facility
Debt Instrument [Line Items]
Maximum leverage ratio			2.75			3.25
Match Group
Debt Instrument [Line Items]
Net unamortized discount (premium)			$ 7,352,000			$ 6,586,000			$ 7,352,000
Debt redeemed			1,535,000,000			$ 1,625,000,000			$ 1,535,000,000
Match Group \| MTCH Term Loan due November 16, 2022 \| Maximum \| Revolving Credit Facility
Debt Instrument [Line Items]
Leverage ratio limiting ability to pay dividends, make distributions, or repurchase stock						4.0
Match Group \| MTCH Credit Facility due December 7, 2023 \| Revolving Credit Facility
Debt Instrument [Line Items]
Annual commitment fee on undrawn funds, basis points (as a percent)						0.25%			0.25%
Match Group \| MTCH Credit Facility due December 7, 2023 \| Maximum \| Revolving Credit Facility
Debt Instrument [Line Items]
Leverage ratio limiting ability to pay dividends, make distributions, or repurchase stock						2.0
ANGI Homeservices \| ANGI Homeservices Credit Facility \| Revolving Credit Facility
Debt Instrument [Line Items]
Borrowings outstanding of credit facility			0			$ 0			$ 0
Annual commitment fee on undrawn funds, basis points (as a percent)						0.25%			0.25%
Debt instrument term				5 years
Maximum borrowing capacity				$ 250,000,000
Senior Notes \| IAC
Debt Instrument [Line Items]
Outstanding balance of debt instrument					$ 517,500,000
Senior Notes \| 6.375% MTCH Senior Notes \| Maximum
Debt Instrument [Line Items]
Maximum leverage ratio						5.0
Senior Notes \| 0.875% Exchangeable Notes due 2026 & 2.00% Exchangeable Notes due 2030 \| IAC
Debt Instrument [Line Items]
Proceeds from issuance of debt after fees and expenses		$ 1,100,000,000
Net unamortized discount (premium)		$ (136,900,000)
Period of reported sale price of common stock (trading days)						5 days
Period of consecutive reported sale price of common stock (trading days)						5 days
Senior Notes \| 2026 Exchangeable Notes \| IAC
Debt Instrument [Line Items]
Stated interest rate (as a percent)						0.875%
Outstanding balance of debt instrument						$ 441,812,000
Effective interest rate (as a percent)						5.35%
Face amount of debt instrument						$ 575,000,000.0
Net unamortized discount (premium)						133,188,000
Debt redeemed			0			$ 575,000,000			$ 0
Senior Notes \| 2030 Exchangeable Notes \| IAC
Debt Instrument [Line Items]
Stated interest rate (as a percent)						2.00%
Outstanding balance of debt instrument						$ 390,057,000					$ 75,000,000
Effective interest rate (as a percent)						6.59%
Face amount of debt instrument						$ 575,000,000.0
Net unamortized discount (premium)						184,943,000
Debt redeemed			0			$ 575,000,000			0
Senior Notes \| 2022 Exchangeable Notes \| IAC
Debt Instrument [Line Items]
Stated interest rate (as a percent)						0.875%
Outstanding balance of debt instrument			463,475,000			$ 473,241,000			463,475,000
Effective interest rate (as a percent)						4.73%
Net unamortized discount (premium)			54,025,000			$ 44,259,000			54,025,000
Period of reported sale price of common stock (trading days)					20 days	5 days
Period of consecutive reported sale price of common stock (trading days)					30 days	5 days
Exchange price on applicable trading day (as a percent)					130.00%
Amount of product relative to last reported price (as a percent)					98.00%
If-converted value in excess of principal						$ 223,700,000			105,000,000.0
Debt redeemed			$ 517,500,000			$ 517,500,000			$ 517,500,000
Senior Notes \| 4.75% Senior Notes \| IAC
Debt Instrument [Line Items]
Stated interest rate (as a percent)			4.75%			4.75%			4.75%
Debt redeemed			$ 34,489,000			$ 0			$ 34,489,000
Premium for debt redeemed	$ 500,000
Accrued interest paid	$ 300,000
Senior Notes \| Match Group \| 6.375% MTCH Senior Notes
Debt Instrument [Line Items]
Stated interest rate (as a percent)						6.375%								6.375%
Debt redeemed			400,000,000			$ 400,000,000			400,000,000
Senior Notes \| Match Group \| 5.00% MTCH Senior Notes
Debt Instrument [Line Items]
Stated interest rate (as a percent)						5.00%							5.00%
Debt redeemed			450,000,000			$ 450,000,000			450,000,000
Senior Notes \| Match Group \| 5.625% MTCH Senior Notes
Debt Instrument [Line Items]
Stated interest rate (as a percent)						5.625%						5.625%
Debt redeemed			0			$ 350,000,000			0			$ 350,000,000
Senior Notes \| IAC FinanceCo 2, Inc.& IAC FinanceCo 3, Inc. \| 0.875% Exchangeable Notes due 2026 & 2.00% Exchangeable Notes due 2030 \| IAC
Debt Instrument [Line Items]
Period of reported sale price of common stock (trading days)		20 days
Period of consecutive reported sale price of common stock (trading days)		30 days
Exchange price on applicable trading day (as a percent)		130.00%
Redemption price (as a percent)		100.00%
Term Loan \| Match Group \| MTCH Term Loan due November 16, 2022
Debt Instrument [Line Items]
Outstanding balance of debt instrument			425,000,000			$ 425,000,000.0			$ 425,000,000
Basis spread on variable rate (as a percent)						4.66%			5.09%
Debt redeemed			425,000,000			$ 425,000,000			$ 425,000,000
Term Loan \| Match Group \| MTCH Term Loan due November 16, 2022 \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)						2.50%
Term Loan \| ANGI Homeservices \| ANGI Term Loan due November 5, 2023
Debt Instrument [Line Items]
Outstanding balance of debt instrument			261,300,000			$ 250,900,000			$ 261,300,000
Basis spread on variable rate (as a percent)						3.53%			4.00%
Debt redeemed			261,250,000			$ 250,938,000			$ 261,250,000
Term Loan \| ANGI Homeservices \| ANGI Term Loan due November 5, 2023 \| Forecast
Debt Instrument [Line Items]
Quarterly repayments of principal							$ 10,300,000	$ 6,900,000		$ 3,400,000
Final principal payment							$ 161,600,000
Term Loan \| ANGI Homeservices \| ANGI Term Loan due November 5, 2023 \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)						1.50%			1.50%
Term Loan \| ANGI Homeservices \| ANGI Term Loan due November 5, 2023 \| Maximum
Debt Instrument [Line Items]
Maximum leverage ratio						4.5
Leverage ratio limiting ability to pay dividends, make distributions, or repurchase stock						4.25
Term Loan \| ANGI Homeservices \| ANGI Term Loan due November 5, 2023 \| Minimum
Debt Instrument [Line Items]
Minimum interest coverage ratio						2.0
Credit Facility \| Match Group \| MTCH Credit Facility due December 7, 2023
Debt Instrument [Line Items]
Outstanding balance of debt instrument			$ 260,000,000.0						$ 260,000,000.0
Borrowings outstanding of credit facility						$ 0
Effective interest rate (as a percent)			4.00%						4.00%
Face amount of debt instrument			$ 500,000,000						$ 500,000,000
Debt redeemed			$ 260,000,000			$ 0			$ 260,000,000
Credit Facility \| Match Group \| MTCH Credit Facility due December 7, 2023 \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)									1.50%
Credit Facility \| Match Group \| MTCH Credit Facility due December 7, 2023 \| Maximum
Debt Instrument [Line Items]
Maximum leverage ratio						5.0
Credit Facility \| Match Group \| MTCH Credit Facility due December 7, 2023 \| Minimum
Debt Instrument [Line Items]
Minimum interest coverage ratio						2.0