Acquisitions (Details) $ / shares in Units, € in Millions					3 Months Ended	6 Months Ended
	May 07, 2018 USD ($) $ / shares shares	Apr. 07, 2017 USD ($)	Jan. 17, 2017 EUR (€)	Jan. 17, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Goodwill					$ 1,148,586,000	$ 1,148,586,000	$ 1,156,288,000
Frutarom
Business Acquisition [Line Items]
Cash to be transferred (in dollars per share) | $ / shares	$ 71.19
Shares to be transferred as consideration (in shares) | shares	0.249
Outstanding fully diluted IFF common stock held by former Frutarom shareholders (percent)						15.80%
Total consideration for acquisition	$ 7,100,000,000
Assumption of debt as consideration	681,000,000
Expected make-whole payments for early debt payoff	$ 35,000,000
PhytoTechnology [Member]
Business Acquisition [Line Items]
Percentage of interests acquired		100.00%
Payments to acquire businesses		$ 54,600,000
Cash acquired		400,000
Contingent consideration, liability		1,400,000
Contingent consideration, liability, maximum		10,000,000
Purchase price exceeds preliminary fair value of net assets		48,000,000
Goodwill		15,200,000
Decrease in administrative expense					$ 600,000
PhytoTechnology [Member] | Trade names
Business Acquisition [Line Items]
Finite-lived intangible assets		$ 4,500,000
Acquired intangible assets useful life		14 years
PhytoTechnology [Member] | Proprietary technology
Business Acquisition [Line Items]
Finite-lived intangible assets		$ 27,500,000
Acquired intangible assets useful life		14 years
PhytoTechnology [Member] | Customer relationships
Business Acquisition [Line Items]
Finite-lived intangible assets		$ 800,000
Acquired intangible assets useful life		2 years
Fragrance Resources [Member]
Business Acquisition [Line Items]
Percentage of interests acquired				100.00%
Payments to acquire businesses			€ 143.4	$ 151,900,000
Cash acquired			13.7	14,400,000
Additional payment for working capital adjustment			1.4	1,500,000
Purchase price exceeds preliminary fair value of net assets				122,000,000
Total consideration for acquisition			€ 142.0	150,500,000
Goodwill				72,000,000
Net deferred tax liability				15,300,000
Fragrance Resources [Member] | Trade Names and Proprietary Technology [Member]
Business Acquisition [Line Items]
Intangible assets acquired				$ 13,600,000
Fragrance Resources [Member] | Trade names
Business Acquisition [Line Items]
Acquired intangible assets useful life			2 years	2 years
Fragrance Resources [Member] | Proprietary technology
Business Acquisition [Line Items]
Acquired intangible assets useful life			5 years	5 years
Fragrance Resources [Member] | Customer relationships
Business Acquisition [Line Items]
Intangible assets acquired				$ 51,700,000
Minimum | Fragrance Resources [Member] | Customer relationships
Business Acquisition [Line Items]
Acquired intangible assets useful life			12 years	12 years
Maximum | Fragrance Resources [Member] | Customer relationships
Business Acquisition [Line Items]
Acquired intangible assets useful life			16 years	16 years
Senior Notes 2007 | Frutarom
Business Acquisition [Line Items]
Shares issued as part of merger consideration (shares) | shares	14,880,000
Assumption of debt as consideration	$ 3,100,000,000
New securities expected to be issued	2,200,000,000
Expected repurchase face amount	250,000,000
Senior Unsecured Bridge Term Loan Credit Facility | Frutarom
Business Acquisition [Line Items]
Line of credit facility, maximum borrowing capacity	$ 5,450,000,000