Marketable Securities Marketable Securities (Details 2) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale
Available-for-sale Securities	$ 390,029	$ 363,542
Cash, fair value	45,416	44,122
Cash, cash equivalents and marketable securities, fair value	435,445	407,664
Cash equivalents
Debt Securities, Available-for-sale
Available-for-sale Securities	130,030	58,054
Short-term marketable securities
Debt Securities, Available-for-sale
Available-for-sale Securities	$ 259,999	$ 305,488

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.

No definition available.

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