Acquisitions (Details)									3 Months Ended		9 Months Ended
	Sep. 26, 2018 USD ($)	Sep. 25, 2018 EUR (€)	Sep. 25, 2018 USD ($)	Sep. 17, 2018 USD ($) shares	May 07, 2018 USD ($) $ / shares shares	Apr. 07, 2017 USD ($)	Jan. 17, 2017 EUR (€)	Jan. 17, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 25, 2018 USD ($)	Jun. 06, 2018 USD ($)	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Revenues									$ 907,548,000	$ 872,940,000	$ 2,758,492,000	$ 2,544,094,000
Operating income									$ 159,268,000	149,000,000	488,633,000	430,750,000
Tangible equity units issued | shares				16,500,000
Tangible equity units proceeds				$ 799,000,000
Interest paid, net of amounts capitalized											$ 91,874,000	48,485,000
Interest rate									5.83%		5.83%
Goodwill									$ 1,152,864,000		$ 1,152,864,000				$ 1,156,288,000
Interest expense									23,914,000	19,221,000	93,755,000	49,584,000
Loss on extinguishment of debt									38,810,000	$ 0	$ 38,810,000	$ 0
Frutarom
Business Acquisition [Line Items]
Assumption of debt as consideration					$ 797,000,000
Cash to be transferred (in dollars per share) | $ / shares					$ 71.19
Shares to be transferred as consideration (in shares) | shares					0.249
Total consideration for acquisition					$ 7,100,000,000
Outstanding fully diluted IFF common stock held by former Frutarom shareholders (percent)											14.00%
Interest expense											$ 38,800,000
Gain on Deal Contingent Foreign Currency Contract											12,500,000
Loss on extinguishment of debt											38,800,000
General and Administrative Expense											26,800,000
PhytoTechnology [Member]
Business Acquisition [Line Items]
Percentage of interests acquired						100.00%
Contingent consideration, liability						$ 1,400,000
Payments to acquire businesses						54,600,000
Cash acquired						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]
Total consideration for acquisition							€ 142,000,000	$ 150,500,000
Percentage of interests acquired								100.00%
Payments to acquire businesses							143,400,000	$ 151,900,000
Cash acquired							13,700,000	14,400,000
Additional payment for working capital adjustment							€ 1,400,000	1,500,000
Purchase price exceeds preliminary fair value of net assets								122,000,000
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]
Expected repurchase face amount					$ 250,000,000
Interest paid, net of amounts capitalized				7,700,000
Expected make-whole payments for early debt payoff				$ 34,900,000
Shares issued as part of merger consideration (shares) | shares					14,900,000
Senior Notes Maturing 2021 through 2026
Business Acquisition [Line Items]
Debt face amount		€ 1,100,000,000.0											$ 1,300,000,000.0
Proceeds from Debt, Net of Issuance Costs		€ 1,092,000,000	$ 1,282,000,000
Senior Notes Maturing 2021 through 2026 | Minimum
Business Acquisition [Line Items]
Interest rate		0.50%											0.50%
Senior Notes Maturing 2021 through 2026 | Maximum
Business Acquisition [Line Items]
Interest rate		1.80%											1.80%
Senior Notes Maturing 2020 through 2048
Business Acquisition [Line Items]
Debt face amount	$ 1,500,000,000.0
Proceeds from Debt, Net of Issuance Costs	$ 1,483,000,000
Senior Notes Maturing 2020 through 2048 | Minimum
Business Acquisition [Line Items]
Interest rate	3.40%
Senior Notes Maturing 2020 through 2048 | Maximum
Business Acquisition [Line Items]
Interest rate	5.00%
Public Offering
Business Acquisition [Line Items]
Shares issued | shares				12,667,947
Consideration received on transaction				$ 1,600,000,000
Loans payable | Term loan credit agreement
Business Acquisition [Line Items]
Debt face amount														$ 350,000,000.0
Designated as Hedging Instrument [Member]
Business Acquisition [Line Items]
Derivative, Gain (Loss) on Derivative, Net				$ (3,900,000)
Designated as Hedging Instrument [Member] | Frutarom
Business Acquisition [Line Items]
Derivative, Gain (Loss) on Derivative, Net									$ (3,900,000)		$ (3,900,000)