Reorganization and Reverse Stock Split - Summary of LLC Units Previously Reported as Redeemable Preferred Units or Temporary Equity Converted Reclassified to Equity (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Stockholders' Equity (Members' Deficit)
Common Stock	$ 5			$ 4
Additional paid-in capital	610,965			584,714
Accumulated other comprehensive loss	(3,929)			(838)
Accumulated deficit	(20,913)			(158,909)
Total Cullinan Stockholders' Equity (Members' Deficit)	586,128			424,971
Non-controlling interests in subsidiaries	0			403
Total Stockholders' Equity (Members' Deficit)	$ 586,128	$ 604,618	$ 419,470	$ 425,374	$ 445,474	$ 458,540	$ 469,699	$ 200,314