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Accounting Policies - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2019
Accounting Policies [Abstract] |
Income tax, Uncertain tax position description | The tax benefits recognized in the financial statements from such positions are then measured based on the largest benefit that has a greater than 50% likelihood of being realized upon settlement.

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- Definition Uncertain Income Tax Position Description + References No definition available. + Details
Name: | iosp_UncertainIncomeTaxPositionDescription
Namespace Prefix: | iosp_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration