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v3.25.3

Segment Reporting - Summary of Segment Reporting related to Selling, General and Administrative Expense and Research and Development Expense (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Segment Reporting Information [Line Items] |  |  |  |
Total selling, general and administrative expenses and research and development expenses | $ 85.6 | $ 77.9 | $ 255.8 | $ 268.0
Operating Segments [Member] | Performance Chemicals [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total selling, general and administrative expenses and research and development expenses | 16.6 | 16.1 | 48.3 | 47.7
Operating Segments [Member] | Fuel Specialties [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total selling, general and administrative expenses and research and development expenses | 25.9 | 24.8 | 77.3 | 79.2
Operating Segments [Member] | Oilfield Services [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total selling, general and administrative expenses and research and development expenses | 24.9 | 25.2 | 73.4 | 91.5
Corporate, Non-Segment [Member] |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |
Total selling, general and administrative expenses and research and development expenses | $ 18.2 | $ 11.8 | $ 56.8 | $ 49.6

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- Definition Selling, general and administrative expense and research and development expense. + References No definition available. + Details
Name: | iosp_SellingGeneralAndAdministrativeExpenseAndResearchAndDevelopmentExpense
Namespace Prefix: | iosp_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_ConsolidationItemsAxis=us-gaap_OperatingSegmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=iosp_PerformanceChemicalsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=iosp_FuelSpecialtiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |