Nature of Business, Basis of Presentation and Going Concern Uncertainty - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Nature Of Business And Basis Of Presentation [LineItems]
Accumulated deficit	$ (245,564)						$ (245,564)		$ (205,578)
Cash,cash equivalents and short-term investments	48,100						48,100		34,400
Working capital	40,300						40,300		$ 29,800
Net Income (Loss)	$ (14,441)	$ (12,718)	$ (12,827)	$ (12,512)	$ (8,461)	$ (6,494)	(39,986)	$ (27,467)
Net cash used in operating activities							$ 31,488	$ 20,581

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

ACHIEVE LIFE SCIENCES, INC. 10-Q