| Document and Entity Information | Aug. 04, 2020 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001054905 |
| Document Type | 8-K |
| Document Period End Date | Aug. 4, 2020 |
| Entity Registrant Name | INNOSPEC INC. |
| Entity File Number | 1-13879 |
| Entity Incorporation State Country Code | DE |
| Entity Tax Identification Number | 98-0181725 |
| 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 |
| Entity Address, Postal Zip Code | 80112 |
| City Area Code | (303) |
| Local Phone Number | 792-5554 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Security 12b Title | Common Stock |
| Trading Symbol | IOSP |
| Security Exchange Name | NASDAQ |
