Condensed Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Total revenue	$ 8,967		$ 8,967
Revenue from Contract with Customer, Product and Service [Extensible List]	idya:CollaborationRevenueMember	idya:CollaborationRevenueMember	idya:CollaborationRevenueMember	idya:CollaborationRevenueMember
Operating expenses
Research and development	$ 10,025	$ 8,923	$ 27,647	$ 25,778
General and administrative	3,938	2,700	11,384	7,174
Total operating expenses	13,963	11,623	39,031	32,952
Loss from operations	(4,996)	(11,623)	(30,064)	(32,952)
Interest income and other income (expense), net	70	654	704	1,758
Net loss	(4,926)	(10,969)	(29,360)	(31,194)
Change in unrealized (losses) gains on marketable securities	(22)	41	(30)	109
Comprehensive loss	$ (4,948)	$ (10,928)	$ (29,390)	$ (31,085)
Net loss per common share, basic and diluted	$ (0.17)	$ (0.54)	$ (1.26)	$ (3.15)
Weighted average number of common shares outstanding used in computing net loss per share, basic and diluted	28,396,670	20,158,223	23,235,218	9,895,574