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Accounting Policies - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2016
Accounting Policies [Line Items] |
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 percent likelihood of being realized upon settlement.
Minimum [Member] |
Accounting Policies [Line Items] |
Short-term investments maturity period | 3 months
Maximum [Member] |
Accounting Policies [Line Items] |
Cash equivalents maturity period | 3 months
Short-term investments maturity period | 12 months

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- Definition Accounting Policies [Line Items] + References No definition available. + Details
Name: | iosp_AccountingPoliciesLineItems
Namespace Prefix: | iosp_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Cash And Cash Equivalents Maturity Period + References No definition available. + Details
Name: | iosp_CashAndCashEquivalentsMaturityPeriod
Namespace Prefix: | iosp_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Short Term Investment Maturity Period + References No definition available. + Details
Name: | iosp_ShortTermInvestmentMaturityPeriod
Namespace Prefix: | iosp_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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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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- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |