Reverse Recapitalization - Narrative (Details) - USD ($) $ in Thousands			3 Months Ended		9 Months Ended
	Sep. 29, 2023	Sep. 28, 2023	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Schedule Of Reverse Recapitalization [Line Items]
Converted shares (in shares)		5,579,266
Stock converted, reverse recapitalization (in shares)	2,278,598
Common stock, shares outstanding (in shares)	21,888,976		35,715,643		35,715,643		21,888,976
Common stock, shares issued (in shares)			35,715,643		35,715,643		21,888,976
Stock options cancelled and converted (in shares)	2,101,760
Transaction costs expensed	$ 7,500		$ 0	$ 3,329	$ 0	$ 3,329
Legacy NKGen
Schedule Of Reverse Recapitalization [Line Items]
Common stock, shares outstanding (in shares)	38,185,814
Common stock, shares issued (in shares)	38,185,814
Options, issued and outstanding (in shares)	5,146,354
Equity Instruments
Schedule Of Reverse Recapitalization [Line Items]
Transaction costs expensed	$ 4,200
Liability Instruments
Schedule Of Reverse Recapitalization [Line Items]
Transaction costs expensed	$ 3,300
Common Stock, Including Convertible Debt Stock
Schedule Of Reverse Recapitalization [Line Items]
Stock converted, reverse recapitalization (in shares)	15,595,260