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Equity Incentive Plans and Stock-Based Compensation (Details 3) (USD $) In Thousands, except Share data, unless otherwise specified | 12 Months Ended | 0 Months Ended
--- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Jun. 22, 2012
Options |  |  |  |
Number of Shares |  |  |  |
Outstanding, at the beginning of the period (in shares) | 11,377,146 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | 13,094,815 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | 14,587,596 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Options granted (in shares) | 2,370,313 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | 2,084,276 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | 7,789,220 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Options exercised (in shares) | (905,464)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | (483,923)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | (221,934)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Stock options forfeited (in shares) | (1,400,349)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | (3,318,022)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | (2,610,812)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Options surrendered in stock option exchange program |  |  | (6,449,255)rmbs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsSurrendedInExchangeOptionsProgramInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Outstanding, at the end of the period (in shares) | 11,441,646 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | 11,377,146 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | 13,094,815 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Vested or expected to vest at the end of the period (in shares) | 10,867,966 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |  |  |
Options exercisable at the end of the period (in shares) | 6,306,425 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |  |  |
Weighted Average Exercise Price |  |  |  |
Outstanding at the beginning of the year (in dollars per shares) | $ 11.32 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | $ 12.79 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | $ 19.73 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Options granted (in dollars per share) | $ 9.63 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | $ 6.09 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | $ 5.81 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Options exercised (in dollars per share) | $ 6.93 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | $ 6.72 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | $ 4.44 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Options forfeited (in dollars per share) | $ 16.13 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | $ 14.51 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | $ 10.91 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Options surrendered in stock option exchange program ( in dollars per share) |  |  | $ 21.11 rmbs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsSurrenderedInStockOptionProgramWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Outstanding at the end of the period (in dollars per shares) | $ 10.73 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | $ 11.32 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | $ 12.79 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Vested or expected to vest at the end of the period (in dollars per share) | $ 10.86 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |  |  |
Options exercisable at the end of the period (in dollars per share) | $ 13.41 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |  |  |
Weighted Average Remaining Contractual Term (in years) |  |  |  |
Outstanding (in years) | 5 years 10 months 24 days |  |  |
Vested or expected to vest (in years) | 5 years 9 months 4 days |  |  |
Options exercisable (in years) | 4 years 1 month 10 days |  |  |
Aggregate Intrinsic Value |  |  |  |
Outstanding | $ 35,073 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |  |  |
Vested or expected to vest | 33,266 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |  |  |
Options exercisable | $ 14,970 us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1 / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |  |  |
Closing stock price (in dollars per share) | $ 11.09 rmbs_EntityClosingStockPrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |  |  |
Total number of in-the-money outstanding (in shares) | 7,824,175 rmbs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsInMoneyOutstandingNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |  |  |
Total number of in-the-money exercisable (in shares) | 3,351,309 rmbs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsInMoneyExercisableNumber / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |  |  |
Stock Option Exchange Program | Options |  |  |  |
Number of Shares |  |  |  |
Options granted (in shares) |  |  | 2,840,986 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = rmbs_StockOptionExchangeProgramMember |
Options surrendered in stock option exchange program |  |  | (6,449,255)rmbs_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsSurrendedInExchangeOptionsProgramInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = rmbs_StockOptionExchangeProgramMember |
Weighted Average Exercise Price |  |  |  |
Options granted (in dollars per share) |  |  |  | $ 5.63 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember / us-gaap_PlanNameAxis = rmbs_StockOptionExchangeProgramMember
Stock Options with Market Condition |  |  |  |
Number of Shares |  |  |  |
Options granted (in shares) |  |  | 1,795,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_PlanNameAxis = rmbs_StockOptionsWithMarketConditionMember |
Outstanding, at the end of the period (in shares) | 1,315,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_PlanNameAxis = rmbs_StockOptionsWithMarketConditionMember | 1,315,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber / us-gaap_PlanNameAxis = rmbs_StockOptionsWithMarketConditionMember |  |

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