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Marketable Securities Marketable Securities (Details 1) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	$ 297,248us-gaap_AvailableForSaleSecurities	$ 270,921us-gaap_AvailableForSaleSecurities
Cash, fair value	20,513rmbs_CashFairValueDisclosure	29,188rmbs_CashFairValueDisclosure
Cash, Cash Equivalents and Short Term Investments, Fair Value Disclosure	317,761rmbs_CashCashEquivalentsAndShortTermInvestmentsFairValueDisclosure	300,109rmbs_CashCashEquivalentsAndShortTermInvestmentsFairValueDisclosure
Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	151,054us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashEquivalentsMember	124,938us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_CashEquivalentsMember
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	$ 146,194us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ShortTermInvestmentsMember	$ 145,983us-gaap_AvailableForSaleSecurities / us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis = us-gaap_ShortTermInvestmentsMember

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

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Namespace Prefix:	rmbs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (aa)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

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- Details

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X

- Details

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