| Document and Entity Information | Aug. 28, 2019 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 28, 2019 |
| Entity Registrant Name | REATA PHARMACEUTICALS INC |
| Entity Central Index Key | 0001358762 |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | true |
| Entity File Number | 001-37785 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 11-3651945 |
| Entity Address, Address Line One | 2801 Gateway Drive |
| Entity Address, Address Line Two | Suite 150 |
| Entity Address, City or Town | Irving |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 75063 |
| City Area Code | 972 |
| Local Phone Number | 865-2219 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of each class | Class A Common Stock, Par Value $0.001 Per Share |
| Trading Symbol | RETA |
| Name of each exchange on which registered | NASDAQ |
