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Convertible Notes (Interest Expense) (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Aug. 16, 2013
Jun. 29, 2009
Interest expense related to notes          
Total interest expense on convertible notes $ 24,820us-gaap_InterestExpense $ 32,885us-gaap_InterestExpense $ 27,510us-gaap_InterestExpense    
Additional paid in capital 1,153,435us-gaap_AdditionalPaidInCapitalCommonStock 1,128,148us-gaap_AdditionalPaidInCapitalCommonStock      
Convertible Senior Notes [Member] | 1.125% Convertible Senior Notes due 2018          
Debt Instrument [Line Items]          
Debt Instrument, Interest Rate, Stated Percentage 1.125%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= rmbs_SeniorOnePointOneTwoFivePercentConvertibleNotesDueTwoThousandEighteenMember
/ us-gaap_LongtermDebtTypeAxis
= rmbs_ConvertibleSeniorNotesMember		 1.125%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= rmbs_SeniorOnePointOneTwoFivePercentConvertibleNotesDueTwoThousandEighteenMember
/ us-gaap_LongtermDebtTypeAxis
= rmbs_ConvertibleSeniorNotesMember		   1.125%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= rmbs_SeniorOnePointOneTwoFivePercentConvertibleNotesDueTwoThousandEighteenMember
/ us-gaap_LongtermDebtTypeAxis
= rmbs_ConvertibleSeniorNotesMember		  
Convertible Senior Notes [Member] | 5% Convertible Senior Notes due 2014          
Debt Instrument [Line Items]          
Debt Instrument, Interest Rate, Stated Percentage 5.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= rmbs_Senior5PercentConvertibleNotesDue2014Member
/ us-gaap_LongtermDebtTypeAxis
= rmbs_ConvertibleSeniorNotesMember		 5.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= rmbs_Senior5PercentConvertibleNotesDue2014Member
/ us-gaap_LongtermDebtTypeAxis
= rmbs_ConvertibleSeniorNotesMember		 5.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= rmbs_Senior5PercentConvertibleNotesDue2014Member
/ us-gaap_LongtermDebtTypeAxis
= rmbs_ConvertibleSeniorNotesMember		    
Convertible notes          
Interest expense related to notes          
Total interest expense on convertible notes 20,259us-gaap_InterestExpense
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		 28,504us-gaap_InterestExpense
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		 23,320us-gaap_InterestExpense
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		    
Additional paid in capital 93,400us-gaap_AdditionalPaidInCapitalCommonStock
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		 93,400us-gaap_AdditionalPaidInCapitalCommonStock
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		      
Convertible notes | 1.125% Convertible Senior Notes due 2018          
Debt Instrument [Line Items]          
Debt Instrument, Interest Rate, Stated Percentage 1.125%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= rmbs_SeniorOnePointOneTwoFivePercentConvertibleNotesDueTwoThousandEighteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		     1.125%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= rmbs_SeniorOnePointOneTwoFivePercentConvertibleNotesDueTwoThousandEighteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		  
Interest expense related to notes          
Coupon interest 1,567us-gaap_InterestExpenseDebt
/ us-gaap_DebtInstrumentAxis
= rmbs_SeniorOnePointOneTwoFivePercentConvertibleNotesDueTwoThousandEighteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		 582us-gaap_InterestExpenseDebt
/ us-gaap_DebtInstrumentAxis
= rmbs_SeniorOnePointOneTwoFivePercentConvertibleNotesDueTwoThousandEighteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		 0us-gaap_InterestExpenseDebt
/ us-gaap_DebtInstrumentAxis
= rmbs_SeniorOnePointOneTwoFivePercentConvertibleNotesDueTwoThousandEighteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		    
Amortization of discount at an additional effective interest rate 6,019us-gaap_AmortizationOfDebtDiscountPremium
/ us-gaap_DebtInstrumentAxis
= rmbs_SeniorOnePointOneTwoFivePercentConvertibleNotesDueTwoThousandEighteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		 2,171us-gaap_AmortizationOfDebtDiscountPremium
/ us-gaap_DebtInstrumentAxis
= rmbs_SeniorOnePointOneTwoFivePercentConvertibleNotesDueTwoThousandEighteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		 0us-gaap_AmortizationOfDebtDiscountPremium
/ us-gaap_DebtInstrumentAxis
= rmbs_SeniorOnePointOneTwoFivePercentConvertibleNotesDueTwoThousandEighteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		    
Additional Effective Interest Rate 5.50%rmbs_AdditionalEffectiveInterestRate
/ us-gaap_DebtInstrumentAxis
= rmbs_SeniorOnePointOneTwoFivePercentConvertibleNotesDueTwoThousandEighteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		 5.50%rmbs_AdditionalEffectiveInterestRate
/ us-gaap_DebtInstrumentAxis
= rmbs_SeniorOnePointOneTwoFivePercentConvertibleNotesDueTwoThousandEighteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		      
Convertible notes | 5% Convertible Senior Notes due 2014          
Debt Instrument [Line Items]          
Debt Instrument, Interest Rate, Stated Percentage         5.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= rmbs_Senior5PercentConvertibleNotesDue2014Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember
Interest expense related to notes          
Coupon interest 3,929us-gaap_InterestExpenseDebt
/ us-gaap_DebtInstrumentAxis
= rmbs_Senior5PercentConvertibleNotesDue2014Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		 8,625us-gaap_InterestExpenseDebt
/ us-gaap_DebtInstrumentAxis
= rmbs_Senior5PercentConvertibleNotesDue2014Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		 8,625us-gaap_InterestExpenseDebt
/ us-gaap_DebtInstrumentAxis
= rmbs_Senior5PercentConvertibleNotesDue2014Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		    
Amortization of discount at an additional effective interest rate $ 8,744us-gaap_AmortizationOfDebtDiscountPremium
/ us-gaap_DebtInstrumentAxis
= rmbs_Senior5PercentConvertibleNotesDue2014Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		 $ 17,126us-gaap_AmortizationOfDebtDiscountPremium
/ us-gaap_DebtInstrumentAxis
= rmbs_Senior5PercentConvertibleNotesDue2014Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		 $ 14,695us-gaap_AmortizationOfDebtDiscountPremium
/ us-gaap_DebtInstrumentAxis
= rmbs_Senior5PercentConvertibleNotesDue2014Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		    
Additional Effective Interest Rate 11.70%rmbs_AdditionalEffectiveInterestRate
/ us-gaap_DebtInstrumentAxis
= rmbs_Senior5PercentConvertibleNotesDue2014Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		 11.70%rmbs_AdditionalEffectiveInterestRate
/ us-gaap_DebtInstrumentAxis
= rmbs_Senior5PercentConvertibleNotesDue2014Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember		 11.70%rmbs_AdditionalEffectiveInterestRate
/ us-gaap_DebtInstrumentAxis
= rmbs_Senior5PercentConvertibleNotesDue2014Member
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_ConvertibleNotesPayableMember