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Marketable Securities (Details) (USD $) In Thousands, unless otherwise specified | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2014 | Dec. 31, 2013
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 | $ 241,472 | $ 359,097
Amortized Cost | 241,527 | 359,112
Gross Unrealized Gains | 3 | 0
Gross Unrealized Losses | (58) | (15)
Cash, fair value | 29,654 | 28,565
Cash, amortized cost | 29,654 | 28,565
Cash, cash equivalents and marketable securities |  |
Fair Value | 271,126 | 387,662
Amortized Cost | 271,181 | 387,677
Gross Unrealized Gains | 3 | 0
Gross Unrealized Losses | (58) | (15)
Money market funds |  |
Cash equivalents and marketable securities |  |
Fair Value | 96,032 | 300,605
Amortized Cost | 96,032 | 300,605
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | 0 | 0
Weighted Rate of Return (as a percent) | 0.01% | 0.01%
Corporate notes, bonds and commercial paper |  |
Cash equivalents and marketable securities |  |
Fair Value | 145,440 | 58,492
Amortized Cost | 145,495 | 58,507
Gross Unrealized Gains | 3 | 0
Gross Unrealized Losses | $ (58) | $ (15)
Weighted Rate of Return (as a percent) | 0.20% | 0.15%

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
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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
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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
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
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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

X
- 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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- 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 + Details
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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 Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- 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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -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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