v3.26.1
STOCK-BASED COMPENSATION PLANS - Narrative (Details)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 06, 2019
USD ($)
shares
Jun. 30, 2026
USD ($)
shares
Jun. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
installment
shares
Jun. 30, 2025
USD ($)
Dec. 31, 2025
shares
Class of Stock [Line Items]            
Stock-based compensation expense | $   $ 3,226 $ 2,676 $ 6,894 $ 4,863  
Granted (in shares)       5,748,775    
Number of options outstanding (in shares)   22,045,665   22,045,665   18,152,258
Unrecognized compensation costs, options | $   $ 13,000   $ 13,000    
Unrecognized compensation costs, options, period for recognition (in years)       2 years 9 months 3 days    
2014 Employee Stock Purchase Plan            
Class of Stock [Line Items]            
Purchase price at the end of offering period 85.00%          
Offering period (in months) 6 months          
Maximum employee subscription rate (as percent) 15.00%          
Maximum employee subscription amount | $ $ 25          
Maximum number of shares per employee in any offering period (in shares) 1,500          
Common stock, reserved for future issuance (in shares)   4,164,300   4,164,300   4,260,647
Number of shares issued (in shares)       96,347    
Share-based Payment Arrangement, Option            
Class of Stock [Line Items]            
Expiration period (in years)       10 years    
Share-based Payment Arrangement, Option | Share-based Compensation Award, Tranche, First Anniversary of Grant Date            
Class of Stock [Line Items]            
Vesting percentage       100.00%    
Share-based Payment Arrangement, Option | Share Based Compensation Award Tranche One            
Class of Stock [Line Items]            
Vesting period       1 year    
Vesting percentage       25.00%    
Share-based Payment Arrangement, Option | Share Based Compensation Award Tranche Two            
Class of Stock [Line Items]            
Vesting period       1 year    
Number of equal quarterly installments | installment       12    
Share-based Payment Arrangement, Option | Minimum            
Class of Stock [Line Items]            
Vesting period       12 months    
Share-based Payment Arrangement, Option | Maximum            
Class of Stock [Line Items]            
Vesting period       48 months    
SARs            
Class of Stock [Line Items]            
Expiration period (in years)       10 years    
SARs | Share-based Compensation Award, Tranche, First Anniversary of Grant Date            
Class of Stock [Line Items]            
Vesting percentage       100.00%    
SARs | Share Based Compensation Award Tranche One            
Class of Stock [Line Items]            
Vesting period       1 year    
Vesting percentage       25.00%    
SARs | Share Based Compensation Award Tranche Two            
Class of Stock [Line Items]            
Vesting period       1 year    
Number of equal quarterly installments | installment       12    
SARs | Minimum            
Class of Stock [Line Items]            
Vesting period       12 months    
SARs | Maximum            
Class of Stock [Line Items]            
Vesting period       48 months    
Inducement Award Program            
Class of Stock [Line Items]            
Granted (in shares)       1,201,575    
Number of options outstanding (in shares)   1,044,875   1,044,875    
Inducement Award Program | Akebia Therapeutics, Inc. 2023 Stock Incentive Plan (the 2023 Plan) (replaces 2014 Plan)            
Class of Stock [Line Items]            
Number of options outstanding (in shares)   3,723,290   3,723,290   3,034,085
Unvested RSUs | Share-based Compensation Award, Tranche, First Anniversary of Grant Date            
Class of Stock [Line Items]            
Vesting percentage       100.00%    
Unvested RSUs | Share Based Compensation Award Tranche One            
Class of Stock [Line Items]            
Vesting percentage       50.00%    
Unvested RSUs | Share Based Compensation Award Tranche Two            
Class of Stock [Line Items]            
Vesting period       6 months    
Vesting percentage       25.00%    
Award vesting grace period (in years)       1 year    
Unvested RSUs | Share-Based Payment Arrangement, Tranche One, First Anniversary After Grant Date, Subjected To Individual Continued Service            
Class of Stock [Line Items]            
Vesting percentage       33.33%    
Unvested RSUs | Share-Based Payment Arrangement, Tranche Two, Second Anniversary After Grant Date, Subjected To Individual Continued Service            
Class of Stock [Line Items]            
Vesting percentage       33.33%    
Unvested RSUs | Share-Based Payment Arrangement, Tranche Three, Third Anniversary After Grant Date, Subjected To Individual Continued Service            
Class of Stock [Line Items]            
Vesting percentage       33.33%    
Unvested RSUs | Share-Based Payment Arrangement, Tranche One, First Anniversary After Grant Date            
Class of Stock [Line Items]            
Vesting percentage       33.33%    
Unvested RSUs | Share-Based Payment Arrangement, Tranche Two, Following First Anniversary After Grant Date            
Class of Stock [Line Items]            
Vesting period       2 years    
Vesting percentage       66.67%    
Number of equal quarterly installments | installment       8    
Award vesting grace period (in years)       1 year    
Restricted Stock Units (RSUs) And Performance Based Restricted Stock Units (PSUs)            
Class of Stock [Line Items]            
Unrecognized compensation costs, options, period for recognition (in years)       1 year 11 months 26 days    
Unrecognized compensation costs, stock | $   $ 10,300   $ 10,300    
Employees | Share-based Payment Arrangement, Option | Akebia Therapeutics, Inc. 2023 Stock Incentive Plan (the 2023 Plan) (replaces 2014 Plan)            
Class of Stock [Line Items]            
Granted (in shares)       4,011,200    
Director | Share-based Payment Arrangement, Option | Akebia Therapeutics, Inc. 2023 Stock Incentive Plan (the 2023 Plan) (replaces 2014 Plan)            
Class of Stock [Line Items]            
Granted (in shares)       536,000