| Document and Entity Information | Nov. 12, 2020 |
| Document and Entity Information [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Nov. 12, 2020 |
| Entity File Number | 001-36485 |
| Entity Registrant Name | ARDELYX, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 26-1303944 |
| Entity Address, Address Line One | 34175 Ardenwood Blvd. |
| Entity Address, City or Town | Fremont |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94555 |
| City Area Code | 510 |
| Local Phone Number | 745-1700 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.0001 |
| Trading Symbol | ARDX |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001437402 |
| Amendment Flag | false |
