CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Operating expenses:
Research and development	$ 36,259	$ 27,391	$ 66,905	$ 79,487
General and administrative	13,768	10,214	26,111	20,874
Total operating expenses	50,027	37,605	93,016	100,361
Loss from operations	(50,027)	(37,605)	(93,016)	(100,361)
Other income (expense):
Interest income	8,071	5,322	13,764	9,830
Other income (expense), net	(72)	69	(116)	176
Net Loss	(42,028)	(32,214)	(79,368)	(90,355)
Net loss attributable to noncontrolling interests	0	0	(192)	(179)
Net loss attributable to common stockholders of Cullinan	(42,028)	(32,214)	(79,176)	(90,176)
Comprehensive income (loss):
Net loss	(42,028)	(32,214)	(79,368)	(90,355)
Unrealized gain (loss) on investments	(145)	(383)	(347)	976
Comprehensive loss	(42,173)	(32,597)	(79,715)	(89,379)
Comprehensive loss attributable to noncontrolling interests	0	0	(192)	(179)
Comprehensive loss attributable to Cullinan	$ (42,173)	$ (32,597)	$ (79,523)	$ (89,200)
Net loss per share attributable to common stockholders of Cullinan:
Net loss per share, basic	$ (0.75)	$ (0.82)	$ (1.61)	$ (2.24)
Net loss per share, diluted	$ (0.75)	$ (0.82)	$ (1.61)	$ (2.24)
Weighted-average shares used in computing net income (loss) per share attributable to common stockholders of Cullinan
Weighted-average common stock outstanding - basic	55,052	39,952	49,031	40,315
Weighted-average common stock outstanding - diluted	55,052	39,952	49,031	40,315