Fair Value Measurements - Loan and Security Agreement (Details) - Solar Capital and Western Alliance Bank Loan Agreement [Member] - USD ($)	1 Months Ended	6 Months Ended
May 31, 2018	Jun. 30, 2018
Fair Value Measurements
Exit Fee	$ 1,500,000
Exit fee payable term (in years)	10 years
Level 3
Fair Value Measurements
Potential payment to Solar Capital Ltd. and Western Alliance Bank		$ 1,500,000
Percentage of increase in risk component		10.00%
Percentage decrease in risk component		10.00%
Fair value fluctuation due to increase in risk component		$ 55,000,000
Fair value fluctuation due to decrease in risk component		$ 55,000,000
Other Current Liabilities
Fair Value Measurements
Estimated fair value of Exit Fee	$ 546,000

Represents the exit fee payable term.

No definition available.

Name:	ardx_ExitFeePayableTerm
Namespace Prefix:	ardx_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of potential milestone payment as a result of FDA approval.

+ References

No definition available.

+ Details

Name:	ardx_FairValueInputsPotentialMilestonePaymentAsResultOfFoodAndDrugsAdministrationApproval
Namespace Prefix:	ardx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The increase (decrease) in a financial instrument as a result of an decrease in a designated risk component that was reasonably possible at the end of the reporting period. Excludes defined benefit plan obligations.

+ References

No definition available.

+ Details

Name:	ardx_IncreaseDecreaseInFinancialInstrumentDueToReasonablyPossibleDecreaseInDesignatedRiskComponent
Namespace Prefix:	ardx_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

The increase (decrease) in a financial instrument as a result of an increase in a designated risk component that was reasonably possible at the end of the reporting period. Excludes defined benefit plan obligations.

+ References

No definition available.

+ Details

Name:	ardx_IncreaseDecreaseInFinancialInstrumentDueToReasonablyPossibleIncreaseInDesignatedRiskComponent
Namespace Prefix:	ardx_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

The reasonably possible percentage of the decrease in the designated risk component used to determine the value of the financial instrument. Excludes defined benefit plan obligations.

+ References

No definition available.

+ Details

Name:	ardx_PercentageOfReasonablyPossibleDecreaseInRiskAssumption
Namespace Prefix:	ardx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The reasonably possible percentage of the increase in the designated risk component used to determine the value of the financial instrument. Excludes defined benefit plan obligations.

+ References

No definition available.

+ Details

Name:	ardx_PercentageOfReasonablyPossibleIncreaseInRiskAssumption
Namespace Prefix:	ardx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Includes, but is not limited to, one-time termination benefits, termination of an operating lease or other contract, consolidating or closing facilities, and relocating employees, and termination benefits associated with an ongoing benefit arrangement. Excludes expenses associated with special or contractual termination benefits, a discontinued operation or an asset retirement obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 5.P.3)
-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140864-122747

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 5.P.4(b))
-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

+ Details

Name:	us-gaap_BusinessExitCosts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value of financial and nonfinancial obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

+ Details

Name:	us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=ardx_SolarCapitalAndWesternAllianceBankLoanAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherCurrentLiabilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: