Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Feb. 09, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Document Annual Report	true
Document Transition Report	false
Current Fiscal Year End Date	--12-31
Document Period End Date	Dec. 31, 2021
Entity File Number	1-13879
Entity Registrant Name	INNOSPEC INC.
Entity Central Index Key	0001054905
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	98-0181725
Entity Address, Postal Zip Code	80112
City Area Code	303
Local Phone Number	792 5554
Security Exchange Name	NASDAQ
Title of 12(b) Security	Common stock
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		24,773,694
Entity Address, Address Line One	8310 South Valley Highway
Entity Address, Address Line Two	Suite 350
Entity Address, City or Town	Englewood
Entity Address, State or Province	CO
Trading Symbol	IOSP
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	Yes
Entity Public Float			$ 1,245
ICFR Auditor Attestation Flag	true
Auditor Name	PricewaterhouseCoopers LLP
Auditor Firm ID	876
Auditor Location	Manchester, United Kingdom