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v2.4.1.9

Income Taxes - Roll-Forward of Unrecognized Tax Benefits and Associated Accrued Interest and Penalties (Detail) (USD $) In Millions, unless otherwise specified | 3 Months Ended |
--- | --- | ---
Mar. 31, 2015 | Dec. 31, 2014
Income Tax Contingency [Line Items] |  |
Opening balance at January 1, 2015 | $ 6.2 us-gaap_UnrecognizedTaxBenefits |
Additions for tax positions of prior periods | 0.1 us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions |
Closing balance at March 31, 2015 | 6.3 us-gaap_UnrecognizedTaxBenefits |
Current | 0 us-gaap_LiabilityForUncertainTaxPositionsCurrent |
Non-current | 6.3 us-gaap_LiabilityForUncertainTaxPositionsNoncurrent | 6.2 us-gaap_LiabilityForUncertainTaxPositionsNoncurrent
Unrecognized Tax Benefits [Member] |  |
Income Tax Contingency [Line Items] |  |
Opening balance at January 1, 2015 | 5.7 us-gaap_UnrecognizedTaxBenefits / us-gaap_ReasonablyPossibleSignificantChangeInUnrecognizedTaxBenefitsByItemAxis = iosp_UnrecognizedTaxBenefitsMember |
Additions for tax positions of prior periods | 0 us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions / us-gaap_ReasonablyPossibleSignificantChangeInUnrecognizedTaxBenefitsByItemAxis = iosp_UnrecognizedTaxBenefitsMember |
Closing balance at March 31, 2015 | 5.7 us-gaap_UnrecognizedTaxBenefits / us-gaap_ReasonablyPossibleSignificantChangeInUnrecognizedTaxBenefitsByItemAxis = iosp_UnrecognizedTaxBenefitsMember |
Current | 0 us-gaap_LiabilityForUncertainTaxPositionsCurrent / us-gaap_ReasonablyPossibleSignificantChangeInUnrecognizedTaxBenefitsByItemAxis = iosp_UnrecognizedTaxBenefitsMember |
Non-current | 5.7 us-gaap_LiabilityForUncertainTaxPositionsNoncurrent / us-gaap_ReasonablyPossibleSignificantChangeInUnrecognizedTaxBenefitsByItemAxis = iosp_UnrecognizedTaxBenefitsMember |
Interest and Penalties [Member] |  |
Income Tax Contingency [Line Items] |  |
Opening balance at January 1, 2015 | 0.5 us-gaap_UnrecognizedTaxBenefits / us-gaap_ReasonablyPossibleSignificantChangeInUnrecognizedTaxBenefitsByItemAxis = iosp_InterestAndPenaltiesMember |
Additions for tax positions of prior periods | 0.1 us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions / us-gaap_ReasonablyPossibleSignificantChangeInUnrecognizedTaxBenefitsByItemAxis = iosp_InterestAndPenaltiesMember |
Closing balance at March 31, 2015 | 0.6 us-gaap_UnrecognizedTaxBenefits / us-gaap_ReasonablyPossibleSignificantChangeInUnrecognizedTaxBenefitsByItemAxis = iosp_InterestAndPenaltiesMember |
Current | 0 us-gaap_LiabilityForUncertainTaxPositionsCurrent / us-gaap_ReasonablyPossibleSignificantChangeInUnrecognizedTaxBenefitsByItemAxis = iosp_InterestAndPenaltiesMember |
Non-current | $ 0.6 us-gaap_LiabilityForUncertainTaxPositionsNoncurrent / us-gaap_ReasonablyPossibleSignificantChangeInUnrecognizedTaxBenefitsByItemAxis = iosp_InterestAndPenaltiesMember |

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- Definition The current portion of the amount recognized for uncertain tax positions as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The noncurrent portion of the amount recognized for uncertain tax positions as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.24) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Unrecognized Tax Benefit -URI http://asc.fasb.org/extlink&oid=6527854 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319 + Details
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- Definition Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15A -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319 + Details
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