| Document and Entity Information | Jun. 15, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | RAMBUS INC |
| Amendment Flag | false |
| Entity Central Index Key | 0000917273 |
| Document Type | 8-K |
| Document Period End Date | Jun. 15, 2021 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 000-22339 |
| Entity Tax Identification Number | 94-3112828 |
| Entity Address, Address Line One | 4453 North First Street |
| Entity Address, Address Line Two | Suite 100 |
| Entity Address, City or Town | San Jose |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 95134 |
| City Area Code | (408) |
| Local Phone Number | 462-8000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, $.001 Par Value |
| Trading Symbol | RMBS |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
