Cash, Cash Equivalents and Marketable Securities - Additional Information (Detail)	12 Months Ended
Dec. 31, 2018
Maximum [Member]
Cash Cash Equivalents And Marketable Securities [Line Items]
Contractual maturities of available for sale securities	1 year

Cash Cash Equivalents And Marketable Securities [Line Items]

No definition available.

Name:	aldx_CashCashEquivalentsAndMarketableSecuritiesLineItems
Namespace Prefix:	aldx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration