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Stock-Based Compensation - Schedule of Information Regarding Restricted Stock Units Outstanding (Detail) (Restricted Stock Units [Member], USD $)
In Millions, except Share data, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Restricted Stock Units [Member]
        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
RSUs outstanding, Number of Shares 564,891us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 668,056us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 708,651us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 407,765us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember
RSUs vested and expected to vest using estimated forfeiture rates, Number of Shares 502,411immr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndExpectedToVestOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 583,711immr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndExpectedToVestOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 588,170immr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndExpectedToVestOutstandingNumber
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		  
RSUs outstanding, Weighted Average Remaining Contractual Life (years) 10 months 2 days 10 months 28 days 1 year 1 month 2 days  
RSUs vested and expected to vest using estimated forfeiture rates, Weighted Average Remaining Contractual Life (years) 9 months 18 days 10 months 21 days 1 year 18 days  
RSUs outstanding, Aggregate Intrinsic Value $ 5.3us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueNonvested
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 $ 6.9us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueNonvested
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 $ 4.9us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueNonvested
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		  
RSUs vested and expected to vest using estimated forfeiture rates, Aggregate Intrinsic Value 4.8immr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 6.1immr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 4.0immr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		  
RSUs outstanding, Fair Value $ 5.3immr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 $ 6.9immr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember		 $ 4.9immr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockUnitsRSUMember