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

Number of customers whose net sales accounted for more than 10% of consolidated net sales.

No definition available.

Name:	iff_EntityWideRevenueMajorCustomerNumberOfCustomers
Namespace Prefix:	iff_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration