Stockholders' Equity - Reserved Shares of Common Stock for Future Issuance (Details) - shares	Jan. 01, 2022	Jan. 01, 2021	Jan. 01, 2020	Dec. 31, 2021	Dec. 31, 2020	Feb. 28, 2014
Class of Stock [Line Items]
Common stock, shares reserved for future issuance (in shares)				26,423,704	23,566,853
Warrant to purchase common stock
Class of Stock [Line Items]
Common stock, shares reserved for future issuance (in shares)				509,611	509,611
Common stock options, RSUs and PSUs outstanding (1)
Class of Stock [Line Items]
Common stock, shares reserved for future issuance (in shares)				16,065,218	14,108,828
Akebia Equity Plans
Class of Stock [Line Items]
Common stock, shares reserved for future issuance (in shares)				4,675,734	3,468,080
2014 Plans
Class of Stock [Line Items]
Common stock, shares reserved for future issuance (in shares)						1,785,000
Increase in common stock, shares reserved for future issuance (in shares)		4,880,775	4,031,376
2014 Plans | Subsequent Event
Class of Stock [Line Items]
Increase in common stock, shares reserved for future issuance (in shares)	5,807,270
Employee Stock Purchase Plan
Class of Stock [Line Items]
Common stock, shares reserved for future issuance (in shares)				5,173,141	5,480,334