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v3.19.1

Marketable Securities (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2019 | Dec. 31, 2018
Cash equivalents and marketable securities |  |
Maximum maturity period of available-for-sale securities (in years) | 3 years | 3 years
Maximum remaining maturity period of available-for-sale securities (in years) | 1 year | 1 year
Fair Value | $ 264,477 | $ 226,708
Amortized Cost | 264,540 | 226,809
Gross Unrealized Gains | 3 | 0
Gross Unrealized Losses | (66) | (101)
Cash, fair value | 41,389 | 51,056
Cash, amortized cost | 41,389 | 51,056
Cash, cash equivalents and marketable securities |  |
Fair Value | 305,866 | 277,764
Amortized Cost | 305,929 | 277,865
Gross Unrealized Gains | 3 | 0
Gross Unrealized Losses | (66) | (101)
Money market funds |  |
Cash equivalents and marketable securities |  |
Fair Value | 10,849 | 10,080
Amortized Cost | 10,849 | 10,080
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | $ 0 | $ 0
Weighted Rate of Return (as a percent) | 2.35% | 2.23%
US Treasury and Government Short-term Debt Securities [Member] |  |
Cash equivalents and marketable securities |  |
Fair Value | $ 41,479 | $ 32,630
Amortized Cost | 41,482 | 32,634
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | $ (3) | $ (4)
Weighted Rate of Return (as a percent) | 2.36% | 2.28%
Corporate notes, bonds and commercial paper |  |
Cash equivalents and marketable securities |  |
Fair Value | $ 212,149 | $ 183,998
Amortized Cost | 212,209 | 184,095
Gross Unrealized Gains | 3 | 0
Gross Unrealized Losses | $ (63) | $ (97)
Weighted Rate of Return (as a percent) | 2.47% | 2.37%

X
- Definition This item represents the weighted rate of return on marketable securities like money market funds, U.S. government bonds and notes, corporate notes, bonds and commercial paper, corporate securities and cash and cash equivalents. + References No definition available. + Details
Name: | rmbs_AvailableForSaleSecuritiesWeightedRateOfReturn
Namespace Prefix: | rmbs_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition This item represents the amortized cost of cash, cash equivalents and marketable securities, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References No definition available. + Details
Name: | rmbs_CashCashEquivalentsAndShortTermInvestmentsAmortizedCostDisclosure
Namespace Prefix: | rmbs_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This element represents the aggregate of cash, cash equivalents and marketable securities reported on the balance sheet at period end measured at fair value by the entity. + References No definition available. + Details
Name: | rmbs_CashCashEquivalentsAndShortTermInvestmentsFairValueDisclosure
Namespace Prefix: | rmbs_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Cash Cash Equivalents And Short Term Investments Unrealized Gains + References No definition available. + Details
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Namespace Prefix: | rmbs_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition Cash Cash Equivalents And Short Term Investments Unrealized Losses + References No definition available. + Details
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Namespace Prefix: | rmbs_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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X
- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. + References No definition available. + Details
Name: | rmbs_CashFairValueDisclosure
Namespace Prefix: | rmbs_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the gross unrealized gains for cash, cash equivalents and marketable securities + References No definition available. + Details
Name: | rmbs_GrossUnrealizedGainOnSecuritiesAndCash
Namespace Prefix: | rmbs_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition This item represents the gross unrealized losses for cash, cash equivalents and marketable securities. + References No definition available. + Details
Name: | rmbs_GrossUnrealizedLossOnSecuritiesAndCash
Namespace Prefix: | rmbs_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Represents the maximum maturity period of securities invested by the entity. + References No definition available. + Details
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Namespace Prefix: | rmbs_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the maximum remaining maturity period of securities invested by the entity. + References No definition available. + Details
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Namespace Prefix: | rmbs_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition -- None. No documentation exists for this element. -- + References No definition available. + Details
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Namespace Prefix: | rmbs_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | debit
Period Type: | instant

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- References No definition available. + Details
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- Details
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- Details
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Namespace Prefix: |
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- Details
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