Credit Facility - Additional Information (Detail) - USD ($)	9 Months Ended
Sep. 30, 2020	Dec. 31, 2019
Line Of Credit Facility [Line Items]
Proceeds from Long-term lines of credit		$ 16,042,500
Debt instrument annual interest rate	9.10%
Interest payment period	May 01, 2021
Interest payment extension period	May 01, 2022
Term loan maturity date	Oct. 01, 2023
Credit facility fee	$ 375,000
Credit facility commitment fee percentage	6.95%
Term loan prepayment term	3% if the term loan is prepaid prior to March 25, 2021 and 1.5% if the term loan is prepaid any time thereafter, but prior to March 25, 2022
Commitment charge	$ 25,000
Transaction costs	$ 273,186
Credit facility, interest rate	12.90%
Maximum [Member]
Line Of Credit Facility [Line Items]
Credit facility prepayment fee percentage	3.00%
Minimum [Member]
Line Of Credit Facility [Line Items]
Credit facility prepayment fee percentage	1.50%
Prime Rate [Member]
Line Of Credit Facility [Line Items]
Debt instrument variable annual interest rate	3.10%
Hercules Credit Facility [Member]
Line Of Credit Facility [Line Items]
Credit facility amount	$ 60,000,000.0
Credit facility amount outstanding	15,000,000.0
Additional credit facility available for borrowing	0
Hercules Credit Facility [Member] \| Maximum [Member]
Line Of Credit Facility [Line Items]
Loan agreement right to purchase aggregate amount of equity securities	2,000,000.0
Hercules Credit Facility [Member] \| Term Loan Advance One [Member]
Line Of Credit Facility [Line Items]
Credit facility amount	5,000,000.0
Hercules Credit Facility [Member] \| Term Loan Advance Two [Member]
Line Of Credit Facility [Line Items]
Proceeds from Long-term lines of credit	15,000,000.0
Hercules Credit Facility [Member] \| Term Loan Advance Three [Member]
Line Of Credit Facility [Line Items]
Proceeds from Long-term lines of credit	15,000,000.0
Hercules Credit Facility [Member] \| Term Loan Advance Four [Member]
Line Of Credit Facility [Line Items]
Proceeds from Long-term lines of credit	15,000,000.0
Hercules Credit Facility [Member] \| Term Loan Advance Five [Member]
Line Of Credit Facility [Line Items]
Proceeds from Long-term lines of credit	$ 10,000,000.0

Line of credit facility, commitment charge.

No definition available.

Name:	aldx_LineOfCreditFacilityCommitmentCharge
Namespace Prefix:	aldx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line of credit facility interest payment extension period.

+ References

No definition available.

+ Details

Name:	aldx_LineOfCreditFacilityInterestPaymentExtensionPeriod
Namespace Prefix:	aldx_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility interest payment period.

+ References

No definition available.

+ Details

Name:	aldx_LineOfCreditFacilityInterestPaymentPeriod
Namespace Prefix:	aldx_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of fee if the term loan is prepaid.

+ References

No definition available.

+ Details

Name:	aldx_LineOfCreditFacilityPrepaymentFeePercentage
Namespace Prefix:	aldx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility, transaction costs.

+ References

No definition available.

+ Details

Name:	aldx_LineOfCreditFacilityTransactionCosts
Namespace Prefix:	aldx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Loan agreement right to purchase aggregate amount of equity securities.

+ References

No definition available.

+ Details

Name:	aldx_LoanAgreementRightToPurchaseAggregateAmountOfEquitySecurities
Namespace Prefix:	aldx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

+ Details

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

- Definition

Amount of the fee for available but unused credit capacity under the credit facility.

+ References

+ Details

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

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of the terms of a credit facility arrangement. Terms typically include interest rate, collateral required, guarantees required, repayment requirements, and restrictions on use of assets and activities of the entity.

+ References

+ Details

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

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The effective interest rate at the end of the reporting period.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The effective interest rate during the reporting period.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Balance Type:
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- Details

Name:	us-gaap_VariableRateAxis=us-gaap_PrimeRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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Namespace Prefix:
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Balance Type:
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- Details

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