Cover Page - shares	3 Months Ended
	Mar. 31, 2020	Apr. 30, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Document Quarterly Report	true
Document Transition Report	false
Current Fiscal Year End Date	--12-31
Document Period End Date	Mar. 31, 2020
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		24,560,830
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