Net Income Per Share - Reconciliation of Shares Used in Computation of Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income attributable to IFF stockholders	$ 86,204	$ 136,377	$ 210,811	$ 245,206
Adjustment related to (increase) decrease in redemption value of redeemable noncontrolling interests in excess of earnings allocated	(1,706)	(513)	4,100	(143)
Net income available to IFF stockholders	$ 84,498	$ 135,864	$ 214,911	$ 245,063
Weighted average common shares outstanding (basic) (in shares)	112,177	111,996	112,130	111,930
Weighted average shares assuming dilution (diluted) (in shares)	113,675	112,872	113,635	113,131
Net income per share - basic (in dollars per share)	$ 0.75	$ 1.21	$ 1.91	$ 2.19
Net income per share - diluted (in dollars per share)	$ 0.74	$ 1.20	$ 1.89	$ 2.16
Stock options and restricted stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Adjustment for assumed dilution (in shares)	335	424	342	393
SPC portion of TEUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Adjustment for assumed dilution (in shares)	1,163	452	1,163	808