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Goodwill - Additional Information (Detail) (USD $)
 12 Months Ended 0 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Oct. 27, 2014
Oct. 26, 2016
Oct. 26, 2015
Goodwill [Line Items]            
Goodwill $ 276,100,000us-gaap_Goodwill $ 187,900,000us-gaap_Goodwill $ 149,000,000us-gaap_Goodwill      
Impairment of goodwill 0us-gaap_GoodwillImpairmentLoss 1,300,000us-gaap_GoodwillImpairmentLoss 1,200,000us-gaap_GoodwillImpairmentLoss      
Deferred consideration payments 49,500,000us-gaap_BusinessCombinationContingentConsiderationLiability 4,600,000us-gaap_BusinessCombinationContingentConsiderationLiability        
Fuel Specialties [Member]            
Goodwill [Line Items]            
Goodwill 229,400,000us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= iosp_FuelSpecialtiesMember		 141,100,000us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= iosp_FuelSpecialtiesMember		 117,600,000us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= iosp_FuelSpecialtiesMember		      
Impairment of goodwill 0us-gaap_GoodwillImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= iosp_FuelSpecialtiesMember		 0us-gaap_GoodwillImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= iosp_FuelSpecialtiesMember		        
Performance Chemicals [Member]            
Goodwill [Line Items]            
Goodwill 46,700,000us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= iosp_PerformanceChemicalsMember		 46,800,000us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= iosp_PerformanceChemicalsMember		 30,100,000us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= iosp_PerformanceChemicalsMember		      
Impairment of goodwill 0us-gaap_GoodwillImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= iosp_PerformanceChemicalsMember		 0us-gaap_GoodwillImpairmentLoss
/ us-gaap_StatementBusinessSegmentsAxis
= iosp_PerformanceChemicalsMember		        
Independence Acquisition [Member]            
Goodwill [Line Items]            
Goodwill 88,100,000us-gaap_Goodwill
/ us-gaap_BusinessAcquisitionAxis
= iosp_IndependenceOilfieldChemicalsLLCMember		          
Date of acquisition Oct. 27, 2014          
Acquired membership interests       100.00%us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
/ us-gaap_BusinessAcquisitionAxis
= iosp_IndependenceOilfieldChemicalsLLCMember		    
Business acquisition, consideration       191,800,000iosp_BusinessAcquisitionNetConsiderationAtFairValue
/ us-gaap_BusinessAcquisitionAxis
= iosp_IndependenceOilfieldChemicalsLLCMember		    
Business acquisition, initial payment       99,000,000us-gaap_BusinessCombinationConsiderationTransferred1
/ us-gaap_BusinessAcquisitionAxis
= iosp_IndependenceOilfieldChemicalsLLCMember		    
Business combination, contingent consideration arrangements, basis for amount As Independence has been in a phase of very rapid growth, the remaining payments are performance related and contingently payable over the next two years based on a multiple of Independence’s annualized earnings before interest, taxes, depreciation and amortization plus a percentage of free cash flow.          
Business acquisition, description Based on the current forecasts for Independence's performance, Innospec will make two deferred consideration payments, with the first one being $45.7 million payable approximately one year after closing, and the second one being $49.5 million payable approximately two years after closing, with a portion of such deferred payments payable, at Innospec's election, in shares of Innospec's common stock.          
Accretion charge 2,400,000us-gaap_AccretionExpense
/ us-gaap_BusinessAcquisitionAxis
= iosp_IndependenceOilfieldChemicalsLLCMember		          
Independence Acquisition [Member] | Forecast [Member]            
Goodwill [Line Items]            
Deferred consideration payments         49,500,000us-gaap_BusinessCombinationContingentConsiderationLiability
/ us-gaap_BusinessAcquisitionAxis
= iosp_IndependenceOilfieldChemicalsLLCMember
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember		 45,700,000us-gaap_BusinessCombinationContingentConsiderationLiability
/ us-gaap_BusinessAcquisitionAxis
= iosp_IndependenceOilfieldChemicalsLLCMember
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember
Independence Acquisition [Member] | Fuel Specialties [Member]            
Goodwill [Line Items]            
Goodwill amortizable for tax purposes $ 0us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount
/ us-gaap_BusinessAcquisitionAxis
= iosp_IndependenceOilfieldChemicalsLLCMember
/ us-gaap_StatementBusinessSegmentsAxis
= iosp_FuelSpecialtiesMember