Name:	aplt_ShareBasedCompensationArrangementByShareBasedPaymentAwardIncreaseInNumberOfSharesReservedAndAvailableForIssuanceNumber
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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Represents the percentage of increase in number of shares reserved and available for issuance at beginning of each fiscal year under the plan.

No definition available.

Name:	aplt_ShareBasedCompensationArrangementByShareBasedPaymentAwardIncreaseInNumberOfSharesReservedAndAvailableForIssuancePercentage
Namespace Prefix:	aplt_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

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.

No definition available.

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

Number of shares authorized for issuance under share-based payment arrangement.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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-Name Accounting Standards Codification
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Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
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Data Type:	xbrli:sharesItemType
Balance Type:	na
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Number of shares issued during the period as a result of an employee stock purchase plan.

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