Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 30, 2018
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Trading Symbol	RETA
Entity Registrant Name	REATA PHARMACEUTICALS INC
Entity Central Index Key	0001358762
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Common Stock A
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		23,990,922
Common Stock B
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		5,727,108