Business Combination - Schedule of Number of Legacy Apexigen Shares (Details) - shares		6 Months Ended	7 Months Ended	12 Months Ended
	Jul. 29, 2022	Jun. 30, 2023	Jul. 29, 2022	Dec. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Exercise of common stock options (Shares)		0
Legacy Apexigen [Member]
Business Acquisition [Line Items]
Common stock, shares	177,132,923				30,521,693
Recapitalization Applied to Convertible Preferred Stock Outstanding at December 31, 2020					145,130,628
Common Stock Shares effected for Brookline Exchange Ratio	18,147,032		18,147,032		3,126,980
Recapitalization applied to Convertible Preferred Stock outstanding at December 31, 2020					14,868,374
Legacy Apexigen [Member] | 2022 Stock Options [Member]
Business Acquisition [Line Items]
Exercise of common stock options (Shares)			702,074
Exercise of common stock restricted awards - 2022			229,556
Exercise of common stock options, Effected for Brookline Exchange Ratio	71,922		71,922
Exercise of common stock restricted awards effected for Brookline exchange ratio	23,518		23,518
Legacy Apexigen [Member] | 2021 Stock Options [Member]
Business Acquisition [Line Items]
Exercise of common stock options (Shares)				548,972
Exercise of common stock options, Effected for Brookline Exchange Ratio				56,238