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v3.20.4

Leases - Additional Information (Detail) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019
Leases [Line Items] |  |
Additional leases that have not yet commenced | $ 0.0 | $ 0.0
Maximum [Member] |  |
Leases [Line Items] |  |
Operating and finance leases, remaining lease terms | 10 years |
Minimum [Member] |  |
Leases [Line Items] |  |
Operating and finance leases, remaining lease terms | 1 year |

X
- Definition Leases. + References No definition available. + Details
Name: | iosp_LeasesLineItems
Namespace Prefix: | iosp_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Lessee, operating and finance leases remaining lease term. + References No definition available. + Details
Name: | iosp_LesseeOperatingAndFinanceLeasesRemainingLeaseTerm
Namespace Prefix: | iosp_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition New leases not yet commenced. + References No definition available. + Details
Name: | iosp_NewLeasesNotYetCommenced
Namespace Prefix: | iosp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |