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v2.4.1.9

Pension Plans - Movements in PBO and Fair Value of Plan Assets (Detail) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Change in PBO: |  |  |
Actuarial losses/(gains) | $ 54.7 us-gaap_DefinedBenefitPlanActuarialGainLoss | $ (6.7)us-gaap_DefinedBenefitPlanActuarialGainLoss | $ (58.5)us-gaap_DefinedBenefitPlanActuarialGainLoss
United Kingdom Plan [Member] |  |  |
Change in PBO: |  |  |
Service cost | 1.7 us-gaap_DefinedBenefitPlanServiceCost / us-gaap_PlanNameAxis = iosp_UkPlanMember | 1.6 us-gaap_DefinedBenefitPlanServiceCost / us-gaap_PlanNameAxis = iosp_UkPlanMember | 1.6 us-gaap_DefinedBenefitPlanServiceCost / us-gaap_PlanNameAxis = iosp_UkPlanMember
Interest cost | 34.7 us-gaap_DefinedBenefitPlanInterestCost / us-gaap_PlanNameAxis = iosp_UkPlanMember | 31.3 us-gaap_DefinedBenefitPlanInterestCost / us-gaap_PlanNameAxis = iosp_UkPlanMember | 32.2 us-gaap_DefinedBenefitPlanInterestCost / us-gaap_PlanNameAxis = iosp_UkPlanMember
Amortization of prior service cost/(credit) | (1.3)us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit / us-gaap_PlanNameAxis = iosp_UkPlanMember | (1.3)us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit / us-gaap_PlanNameAxis = iosp_UkPlanMember | (1.3)us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit / us-gaap_PlanNameAxis = iosp_UkPlanMember
Benefits paid | (47.6)us-gaap_DefinedBenefitPlanBenefitsPaid / us-gaap_PlanNameAxis = iosp_UkPlanMember | (39.4)us-gaap_DefinedBenefitPlanBenefitsPaid / us-gaap_PlanNameAxis = iosp_UkPlanMember |
Fair value of plan assets: |  |  |
Opening balance | 790.3 us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsCurrentAndNoncurrent / us-gaap_PlanNameAxis = iosp_UkPlanMember | 768.6 us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsCurrentAndNoncurrent / us-gaap_PlanNameAxis = iosp_UkPlanMember |
Benefits paid | (47.6)us-gaap_DefinedBenefitPlanBenefitsPaid / us-gaap_PlanNameAxis = iosp_UkPlanMember | (39.4)us-gaap_DefinedBenefitPlanBenefitsPaid / us-gaap_PlanNameAxis = iosp_UkPlanMember |
Actual contributions by employer | 11.4 us-gaap_DefinedBenefitPlanContributionsByEmployer / us-gaap_PlanNameAxis = iosp_UkPlanMember | 10.8 us-gaap_DefinedBenefitPlanContributionsByEmployer / us-gaap_PlanNameAxis = iosp_UkPlanMember |
Actual return on assets | 161.7 us-gaap_DefinedBenefitPlanActualReturnOnPlanAssets / us-gaap_PlanNameAxis = iosp_UkPlanMember | 35.5 us-gaap_DefinedBenefitPlanActualReturnOnPlanAssets / us-gaap_PlanNameAxis = iosp_UkPlanMember |
Exchange effect | (53.5)us-gaap_DefinedBenefitPlanForeignCurrencyExchangeRateChangesPlanAssets / us-gaap_PlanNameAxis = iosp_UkPlanMember | 14.8 us-gaap_DefinedBenefitPlanForeignCurrencyExchangeRateChangesPlanAssets / us-gaap_PlanNameAxis = iosp_UkPlanMember |
Closing balance | 862.3 us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsCurrentAndNoncurrent / us-gaap_PlanNameAxis = iosp_UkPlanMember | 790.3 us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsCurrentAndNoncurrent / us-gaap_PlanNameAxis = iosp_UkPlanMember | 768.6 us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsCurrentAndNoncurrent / us-gaap_PlanNameAxis = iosp_UkPlanMember
German Plan [Member] |  |  |
Change in PBO: |  |  |
Opening balance | 9.6 us-gaap_DefinedBenefitPlanBenefitObligation / us-gaap_PlanNameAxis = iosp_GermanPlanMember | 9.3 us-gaap_DefinedBenefitPlanBenefitObligation / us-gaap_PlanNameAxis = iosp_GermanPlanMember |
Service cost | 0.2 us-gaap_DefinedBenefitPlanServiceCost / us-gaap_PlanNameAxis = iosp_GermanPlanMember | 0.2 us-gaap_DefinedBenefitPlanServiceCost / us-gaap_PlanNameAxis = iosp_GermanPlanMember | 0.1 us-gaap_DefinedBenefitPlanServiceCost / us-gaap_PlanNameAxis = iosp_GermanPlanMember
Interest cost | 0.3 us-gaap_DefinedBenefitPlanInterestCost / us-gaap_PlanNameAxis = iosp_GermanPlanMember | 0.3 us-gaap_DefinedBenefitPlanInterestCost / us-gaap_PlanNameAxis = iosp_GermanPlanMember | 0.3 us-gaap_DefinedBenefitPlanInterestCost / us-gaap_PlanNameAxis = iosp_GermanPlanMember
Amortization of prior service cost/(credit) | 0 us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit / us-gaap_PlanNameAxis = iosp_GermanPlanMember | (0.1)us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit / us-gaap_PlanNameAxis = iosp_GermanPlanMember | 0 us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit / us-gaap_PlanNameAxis = iosp_GermanPlanMember
Benefits paid | (0.2)us-gaap_DefinedBenefitPlanBenefitsPaid / us-gaap_PlanNameAxis = iosp_GermanPlanMember | (0.2)us-gaap_DefinedBenefitPlanBenefitsPaid / us-gaap_PlanNameAxis = iosp_GermanPlanMember |
Actuarial losses/(gains) | 1.8 us-gaap_DefinedBenefitPlanActuarialGainLoss / us-gaap_PlanNameAxis = iosp_GermanPlanMember | (0.4)us-gaap_DefinedBenefitPlanActuarialGainLoss / us-gaap_PlanNameAxis = iosp_GermanPlanMember |
Exchange effect | (1.3)us-gaap_DefinedBenefitPlanForeignCurrencyExchangeRateChangesBenefitObligation / us-gaap_PlanNameAxis = iosp_GermanPlanMember | 0.5 us-gaap_DefinedBenefitPlanForeignCurrencyExchangeRateChangesBenefitObligation / us-gaap_PlanNameAxis = iosp_GermanPlanMember |
Closing balance | 10.4 us-gaap_DefinedBenefitPlanBenefitObligation / us-gaap_PlanNameAxis = iosp_GermanPlanMember | 9.6 us-gaap_DefinedBenefitPlanBenefitObligation / us-gaap_PlanNameAxis = iosp_GermanPlanMember | 9.3 us-gaap_DefinedBenefitPlanBenefitObligation / us-gaap_PlanNameAxis = iosp_GermanPlanMember
Fair value of plan assets: |  |  |
Benefits paid | (0.2)us-gaap_DefinedBenefitPlanBenefitsPaid / us-gaap_PlanNameAxis = iosp_GermanPlanMember | (0.2)us-gaap_DefinedBenefitPlanBenefitsPaid / us-gaap_PlanNameAxis = iosp_GermanPlanMember |
Pension Benefit Obligation [Member] | United Kingdom Plan [Member] |  |  |
Change in PBO: |  |  |
Opening balance | 819.8 us-gaap_DefinedBenefitPlanBenefitObligation / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_PlanNameAxis = iosp_UkPlanMember | 805.3 us-gaap_DefinedBenefitPlanBenefitObligation / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_PlanNameAxis = iosp_UkPlanMember |
Service cost | 1.7 us-gaap_DefinedBenefitPlanServiceCost / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_PlanNameAxis = iosp_UkPlanMember | 1.6 us-gaap_DefinedBenefitPlanServiceCost / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_PlanNameAxis = iosp_UkPlanMember |
Interest cost | 34.7 us-gaap_DefinedBenefitPlanInterestCost / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_PlanNameAxis = iosp_UkPlanMember | 31.3 us-gaap_DefinedBenefitPlanInterestCost / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_PlanNameAxis = iosp_UkPlanMember |
Benefits paid | (47.6)us-gaap_DefinedBenefitPlanBenefitsPaid / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_PlanNameAxis = iosp_UkPlanMember | (39.4)us-gaap_DefinedBenefitPlanBenefitsPaid / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_PlanNameAxis = iosp_UkPlanMember |
Actuarial losses/(gains) | 59.3 us-gaap_DefinedBenefitPlanActuarialGainLoss / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_PlanNameAxis = iosp_UkPlanMember | 5.9 us-gaap_DefinedBenefitPlanActuarialGainLoss / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_PlanNameAxis = iosp_UkPlanMember |
Exchange effect | (50.8)us-gaap_DefinedBenefitPlanForeignCurrencyExchangeRateChangesBenefitObligation / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_PlanNameAxis = iosp_UkPlanMember | 15.1 us-gaap_DefinedBenefitPlanForeignCurrencyExchangeRateChangesBenefitObligation / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_PlanNameAxis = iosp_UkPlanMember |
Closing balance | 817.1 us-gaap_DefinedBenefitPlanBenefitObligation / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_PlanNameAxis = iosp_UkPlanMember | 819.8 us-gaap_DefinedBenefitPlanBenefitObligation / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_PlanNameAxis = iosp_UkPlanMember |
Fair value of plan assets: |  |  |
Benefits paid | $ (47.6)us-gaap_DefinedBenefitPlanBenefitsPaid / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_PlanNameAxis = iosp_UkPlanMember | $ (39.4)us-gaap_DefinedBenefitPlanBenefitsPaid / us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis = us-gaap_PensionPlansDefinedBenefitMember / us-gaap_PlanNameAxis = iosp_UkPlanMember |

X
- Definition The difference between fair value of plan assets at the end of the period and the fair value at the beginning of the period, adjusted for contributions and payments of benefits during the period, and after adjusting for taxes and other expenses, as applicable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Actual Return on Plan Assets (Component of Net Periodic Postretirement Benefit Cost) -URI http://asc.fasb.org/extlink&oid=6504192 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Actual Return on Plan Assets (Component of Net Periodic Pension Cost) -URI http://asc.fasb.org/extlink&oid=6504226 + Details
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- Definition Amount of gain (loss) related to change in benefit obligation resulting from changes in actuarial assumptions, for example, but not limited to, interest, mortality, employee turnover, salary, and temporary deviation from the substantive plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Glossary Gain or Loss -URI http://asc.fasb.org/extlink&oid=6514294 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Glossary Gain or Loss -URI http://asc.fasb.org/extlink&oid=6749293 + Details
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- Definition The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition This represents the entire assets recognized in the balance sheet that are associated with the defined benefit plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.10) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=21915240&loc=d3e1703-114919 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.10) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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- Definition 1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Projected Benefit Obligation -URI http://asc.fasb.org/extlink&oid=6522206 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Accumulated Postretirement Benefit Obligation -URI http://asc.fasb.org/extlink&oid=6503904 + Details
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- Definition The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Postretirement Benefits -URI http://asc.fasb.org/extlink&oid=6521376 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Glossary Benefits -URI http://asc.fasb.org/extlink&oid=6506267 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Glossary Benefits -URI http://asc.fasb.org/extlink&oid=6506309 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(6) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(5) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition The increase in the fair value of plan assets from contributions made by the employer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition Amount of gain (loss) from foreign currency exchange rate changes for benefit obligation for plans of a foreign operation whose functional currency is not the reporting currency. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(5) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition The amount of increase or decrease in plan assets attributed to foreign currency changes. The effects of foreign currency exchange rate changes that are to be disclosed are those applicable to plans of a foreign operation whose functional currency is not the reporting currency. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(2) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Service Cost (Component of Net Periodic Pension Cost) -URI http://asc.fasb.org/extlink&oid=6525008 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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