Preferred and Common Stock - Additional Information (Details) - USD ($)		1 Months Ended				3 Months Ended				9 Months Ended
	Jan. 16, 2021	Jun. 30, 2021	Apr. 30, 2021	Oct. 31, 2020	Feb. 29, 2020	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2021	Jul. 07, 2021	May 10, 2021	Dec. 31, 2020	Jan. 31, 2020
Class Of Stock [Line Items]
Preferred stock, shares authorized						25,000,000				25,000,000			25,000,000	25,000,000
Preferred stock, par value per share						$ 0.01				$ 0.01			$ 0.01	$ 0.01
Common stock, shares authorized						250,000,000				250,000,000			250,000,000	250,000,000
Common stock, par or stated value per share						$ 0.01				$ 0.01			$ 0.01	$ 0.01
Gross proceeds from issuance of common stock				$ 135,100,000
Common stock, voting rights										The holders of the Company’s common stock are entitled to one vote for each share of common stock.
Common Stock
Class Of Stock [Line Items]
Shares issued and sold				5,750,000		2,912,557	1,761,285	2,795,700	12,176,471
Public offering price per share				$ 23.50
Net proceeds from sale of common stock				$ 126,600,000	$ 188,300,000
Issuance of common stock for success payment liability, Shares							349,650
Prime Medicine Inc | Common Stock
Class Of Stock [Line Items]
Shares issued and sold				200,307
Broad Institute
Class Of Stock [Line Items]
Issuance of common stock for success payment liability, Shares		174,825
Success payments liability												$ 15,000,000.0
Harvard Institute
Class Of Stock [Line Items]
Issuance of common stock for success payment liability, Shares		174,825
Success payments liability												$ 15,000,000.0
Jeffries LLC Amended Sales Agreement
Class Of Stock [Line Items]
Gross proceeds from issuance of common stock										$ 190,500,000
Jeffries LLC Amended Sales Agreement | Common Stock
Class Of Stock [Line Items]
Shares issued and sold										1,765,833
Public offering price per share						$ 107.88				$ 107.88
Jeffries LLC Sales Agreement
Class Of Stock [Line Items]
Stock sold during period shares, new issues										2,908,009
Public offering price per share						$ 103.16				$ 103.16
Gross proceeds from issuance of common stock										$ 300,000,000.0
Jeffries LLC Sales Agreement and Amended Sales Agreement
Class Of Stock [Line Items]
Gross proceeds from issuance of common stock										$ 490,500,000
IPO | Common Stock
Class Of Stock [Line Items]
Shares issued and sold					12,176,471
Public offering price per share					$ 17.00
Gross proceeds from issuance of common stock					$ 207,000,000.0
Net proceeds from sale of common stock					$ 188,300,000
Shares issued upon conversion of preferred stock					29,127,523
Underwriters Option | Common Stock
Class Of Stock [Line Items]
Shares issued and sold				750,000	1,588,235
Private Placement
Class Of Stock [Line Items]
Gross proceeds from issuance of common stock	$ 260,000,000.0
Private Placement | Common Stock
Class Of Stock [Line Items]
Shares issued and sold	2,795,700
Public offering price per share	$ 93.00
Net proceeds from sale of common stock	$ 252,000,000.0
At-The-Market | Jeffries LLC Amended Sales Agreement
Class Of Stock [Line Items]
Aggregate gross proceeds of shares authorized under ATM sales agreement											$ 500,000,000.0
At-The-Market | Jeffries LLC Sales Agreement | Maximum
Class Of Stock [Line Items]
Aggregate gross proceeds of shares authorized under ATM sales agreement			$ 300,000,000.0
Commission rate			3.00%