v3.26.1
STOCK-BASED COMPENSATION PLANS - Schedule of Equity Plans (Details) - shares
Mar. 31, 2026
Dec. 31, 2025
Jun. 10, 2025
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Number of options outstanding (in shares) 21,871,531 18,152,258  
Inducement Award Program      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Number of options outstanding (in shares) 858,775    
Keryx Equity Plans      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Awards outstanding (in shares) 91,696 148,860  
Additional awards available for grant (in shares) 0 0  
Akebia Therapeutics, Inc. 2014 Incentive Plan, as amended (the 2014 Plan)      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Awards outstanding (in shares) 7,634,941 8,412,898  
Additional awards available for grant (in shares) 0 0  
Akebia Therapeutics, Inc. 2014 Incentive Plan, as amended (the 2014 Plan) | Inducement Award Program      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Number of options outstanding (in shares) 956,825 1,050,525  
Akebia Therapeutics, Inc. 2023 Stock Incentive Plan (the 2023 Plan) (replaces 2014 Plan), as amended      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Awards outstanding (in shares) 23,224,380 15,913,729  
Additional awards available for grant (in shares) 16,482,848 24,723,655  
Akebia Therapeutics, Inc. 2023 Stock Incentive Plan (the 2023 Plan) (replaces 2014 Plan), as amended | Inducement Award Program      
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]      
Additional awards available for grant (in shares)     18,900,000
Number of options outstanding (in shares) 3,787,674 3,034,085