CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Statement [Abstract]
Revenue	$ 18,943	$ 0	[1]
Type of revenue [Extensible List]	us-gaap:LicenseMember	us-gaap:LicenseMember
Operating expenses:
Research and development	$ 57,751	$ 43,211	[1]
General and administrative	29,146	17,124	[1]
Total operating expenses	86,897	60,335	[1]
Loss from operations	(67,954)	(60,335)	[1]
Other income (expense):
Interest income	477	888	[1]
Other income (expense), net	(8)	(11)	[1]
Net loss	(67,485)	(59,458)	[1]
Net loss attributable to noncontrolling interest	(1,915)	(7,659)	[1]
Net loss attributable to common stockholders of Cullinan	$ (65,570)	$ (51,799)	[1],[2]
Net loss per share, basic and diluted	$ (1.52)	$ (2.60)	[1],[2]
Total weighted-average shares used in computing net loss per share, basic and diluted	43,077,330	19,887,307	[1],[2]
Comprehensive loss:
Net loss	$ (67,485)	$ (59,458)	[1]
Unrealized gain/(loss) on investments	(836)	2	[1]
Comprehensive loss	(68,321)	(59,456)	[1]
Comprehensive loss attributable to noncontrolling interest	(1,915)	(7,659)	[1]
Comprehensive loss attributable to Cullinan	$ (66,406)	$ (51,797)	[1]

[1] The shares and per share amounts for the year ended December 31, 2020 were derived from the consolidated financial statements as of that date and were retroactively adjusted as a result of the Reorganization and Reverse Stock Split. See Note 3 to the consolidated financial statements for additional details.

[2] The shares and per share amounts for the year ended December 31, 2020 were derived from the consolidated financial statements as of that date and were retroactively adjusted as a result of the Reorganization and Reverse Stock Split. See Note 3 to the for additional details.