Liability Related to Sale of Future Royalties - Rollforward of Liability Related to Sale of Future Royalties (Details) - USD ($) $ in Thousands		9 Months Ended
Feb. 25, 2021	Sep. 30, 2021	Sep. 30, 2020
Contractual Arrangement, Royalties Agreement, Liability, Noncurrent [Roll Forward]
Liability related to sale of future royalties, net — beginning balance		$ 0
Proceeds from sale of future royalties, net	$ 44,800	44,783	$ 0
MTPC royalties payable		(425)
Non-cash interest expense recognized		6,779	$ 0
Liability related to sale of future royalties, net — ending balance	$ 44,800	$ 51,137

Contractual Arrangement, Royalties Agreement, Liability, Noncurrent

No definition available.

Name:	akba_ContractualArrangementRoyaltiesAgreementLiabilityNoncurrent
Namespace Prefix:	akba_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Contractual Arrangement, Royalties Agreement, Liability, Noncurrent

No definition available.

Name:	akba_ContractualArrangementRoyaltiesAgreementLiabilityNoncurrentRollForward
Namespace Prefix:	akba_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Contractual Arrangement, Royalties Agreement, Noncash Interest Expense (Income)

No definition available.

Name:	akba_ContractualArrangementRoyaltiesAgreementNoncashInterestExpenseIncome
Namespace Prefix:	akba_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Contractual Arrangement, Royalties Agreement, Royalties, Earned And Payable

No definition available.

Name:	akba_ContractualArrangementRoyaltiesAgreementRoyaltiesEarnedAndPayable
Namespace Prefix:	akba_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Proceeds From Contractual Arrangement, Royalties Agreement, Sale Of Future Royalties

No definition available.

Name:	akba_ProceedsFromContractualArrangementRoyaltiesAgreementSaleOfFutureRoyalties
Namespace Prefix:	akba_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration