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v3.19.3.a.u2

Concentrations Of Credit Risk - Additional Information (Detail) - Customer | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Risks and Uncertainties [Abstract] |  |  |
Number of customers that accounted for more than 10% of consolidated net sales | 0 | 0 | 1

X
- Definition Number of customers whose net sales accounted for more than 10% of consolidated net sales. + References No definition available. + Details
Name: | iff_EntityWideRevenueMajorCustomerNumberOfCustomers
Namespace Prefix: | iff_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_RisksAndUncertaintiesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration