Stockholders' Equity - Equity Incentive Plans (Details) - $ / shares shares in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2015	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	May 25, 2021
Class Of Stock [Line Items]
Percentage of annual increase in shares reserved for issuance				5.00%
Number of common stock shares provided for issuance of stock awards to its employees		14,993		14,993
2019 incentive award plan
Class Of Stock [Line Items]
Shares of common stock reserved for issuance		1,954,150		1,954,150
2015 plan
Class Of Stock [Line Items]
Options expiration term	10 years
Options vesting period	4 years
2015 plan | Private Oncternal
Class Of Stock [Line Items]
Number of common stock shares provided for issuance of stock awards to its employees	631,120
2019 Plan And Inducement Plan
Class Of Stock [Line Items]
Number of common stock shares provided for issuance of stock awards to its employees		2,103,953		2,103,953
2019 plan
Class Of Stock [Line Items]
Options expiration term	10 years
Options vesting period	4 years
Inducement Plan
Class Of Stock [Line Items]
Number of common stock shares provided for issuance of stock awards to its employees						2,800,000
2019 and 2015 plan
Class Of Stock [Line Items]
Weighted average grant date fair value per share of option grants				$ 1.43	$ 4.74
Weighted average exercise price, exercised		$ 3.89	$ 3.89