Portion of Deferred Compensation Plan to be paid out in shares.

No definition available.

Name:	iff_AdjustmentsToAdditionalPaidInCapitalDeferredCompensation
Namespace Prefix:	iff_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Defined contribution plan, matching participant contribution, average percentage on compensation

+ References

No definition available.

+ Details

Name:	iff_DefinedContributionPlanMatchingParticipantContributionAveragePercentageOnCompensation
Namespace Prefix:	iff_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined contribution plan matching participant contribution percentage on compensation range

+ References

No definition available.

+ Details

Name:	iff_DefinedContributionPlanMatchingParticipantContributionPercentageOnCompensationRange
Namespace Prefix:	iff_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined contribution plan, matching participant contribution, percentage on compensation, range high

+ References

No definition available.

+ Details

Name:	iff_DefinedContributionPlanMatchingParticipantContributionPercentageOnCompensationRangeHigh
Namespace Prefix:	iff_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined contribution plan, matching participant contribution, percentage on compensation, range low

+ References

No definition available.

+ Details

Name:	iff_DefinedContributionPlanMatchingParticipantContributionPercentageOnCompensationRangeLow
Namespace Prefix:	iff_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined contribution plan, percentage of matching contribution if compensation percentage below low range

+ References

No definition available.

+ Details

Name:	iff_DefinedContributionPlanPercentageOfMatchingContributionIfCompensationPercentageBelowLowRange
Namespace Prefix:	iff_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined contribution plan, percentage of matching contribution if compensation percentage between high range and low range

+ References

No definition available.

+ Details

Name:	iff_DefinedContributionPlanPercentageOfMatchingContributionIfCompensationPercentageBetweenHighRangeAndLowRange
Namespace Prefix:	iff_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Defined contribution plan, percentage of matching contribution if compensation percentage reaches average rate

+ References

No definition available.

+ Details

Name:	iff_DefinedContributionPlanPercentageOfMatchingContributionIfCompensationPercentageReachesAverageRate
Namespace Prefix:	iff_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of Active Employees with Pension and or Other Retirement Benefit Plans Covered

+ References

No definition available.

+ Details

Name:	iff_PercentageofActiveEmployeeswithPensionandorOtherRetirementBenefitPlansCovered
Namespace Prefix:	iff_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Carrying amount as of the balance sheet date of amounts which could be received based on the terms of the insurance contract upon surrendering life policies owned by the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 4
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=118951113&loc=d3e6812-107765

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 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

+ References

+ Details

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

- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(01)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(ii)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

+ Details

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

- 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_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

+ Details

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

- Definition

Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans, classified as noncurrent.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109237824&loc=d3e1703-114919

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109237824&loc=d3e1731-114919

Reference 4: 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(24))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

Name:	us-gaap_DeferredCompensationArrangementWithIndividualPostretirementBenefitsByTypeOfDeferredCompensationAxis=us-gaap_DeferredCompensationArrangementWithIndividualByTypeOfCompensationPensionAndOtherPostretirementBenefitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RetirementPlanSponsorLocationAxis=country_US
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_FixedIncomeSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RetirementPlanTaxStatusAxis=us-gaap_QualifiedPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RetirementPlanTaxStatusAxis=us-gaap_NonqualifiedPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RetirementPlanSponsorLocationAxis=us-gaap_ForeignPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_RealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=iff_AlternativeTypeOfInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Employee Benefits - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Percentage of Active Employees with Pension and or Other Retirement Benefit Plans Covered	20.00%
Percentage of matching contribution if compensation percentage below low range	100.00%
Matching participant's contribution, percentage on compensation	4.00%
Percentage of matching contribution if compensation percentage between high range and low range	75.00%
Matching participant's contribution, percentage on compensation, range low	4.00%
Matching participant's contribution, percentage on compensation, range high	8.00%
Percentage of employees eligible to accrue benefits under the defined plan	50.00%
Matching participant's contribution, average percentage on compensation	6.00%
Retirement liabilities	$ 265,370,000	$ 227,172,000
Capital in excess of par value related to Deferred Compensation Plan	28,200,000	22,200,000
Total cash surrender value of life insurance contracts	47,578,000	43,179,000
Deferred Compensation Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Retirement liabilities	50,900,000	43,600,000
Pension Plan [Member] \| U.S Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	620,654,000	562,043,000	$ 602,783,000
Retirement liabilities	49,292,000	46,519,000
Contribution to the plans	3,683,000	$ 3,524,000
Pension Plan [Member] \| U.S Plans [Member] \| Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target percentage of investment in equity securities		20.00%
Pension Plan [Member] \| U.S Plans [Member] \| Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Target percentage of investment in equity securities		80.00%
Pension Plan [Member] \| U.S Plans [Member] \| Qualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Contribution to the plans	0
Pension Plan [Member] \| U.S Plans [Member] \| Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Contribution to the plans	3,700,000
Pension Plan [Member] \| Non-U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	1,099,084,000	$ 957,935,000	973,061,000
Retirement liabilities	143,040,000	114,705,000
Contribution to the plans	$ 20,031,000	18,238,000
Pension Plan [Member] \| Non-U.S. Plans [Member] \| Real Estate [Member] \| Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target percentage of investment in equity securities	15.00%
Pension Plan [Member] \| Non-U.S. Plans [Member] \| Equity Securities [Member] \| Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target percentage of investment in equity securities	15.00%
Pension Plan [Member] \| Non-U.S. Plans [Member] \| Fixed Income Securities [Member] \| Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target percentage of investment in equity securities	35.00%
Pension Plan [Member] \| Non-U.S. Plans [Member] \| Alternative Type of Investments [Member] \| Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target percentage of investment in equity securities	35.00%
Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	$ 64,174,000	$ 59,625,000	$ 82,714,000
Contribution to the plans	$ 2,700,000