Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Total revenue	$ 19,538
Revenue from Contract with Customer, Product and Service [Extensible List]	idya:CollaborationRevenuesMember	idya:CollaborationRevenuesMember	idya:CollaborationRevenuesMember
Operating expenses
Research and development	$ 39,698	$ 34,319	$ 31,749
General and administrative	15,184	9,952	4,668
Total operating expenses	54,882	44,271	36,417
Loss from operations	(35,344)	(44,271)	(36,417)
Interest income and other income (expense), net	849	2,296	2,071
Net loss	(34,495)	(41,975)	(34,346)
Change in unrealized (losses) gains on marketable securities	(58)	96	(30)
Comprehensive loss	$ (34,553)	$ (41,879)	$ (34,376)
Net loss per common share, basic and diluted	$ (1.40)	$ (3.36)	$ (35.92)
Weighted-average number of common shares outstanding used in computing net loss per share, basic and diluted	24,721,775	12,496,957	956,252

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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