CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating expenses:
Research and development	$ 148,156	$ 91,948
General and administrative	42,493	40,189
Total operating expenses	190,649	132,137
Impairment of long-lived assets	440	0
Gain on sale of Cullinan Pearl	0	276,785
Income (loss) from operations	(191,089)	144,648
Other income (expense):
Interest income	21,627	6,611
Other income (expense), net	239	57
Net income (loss) before income taxes	(169,223)	151,316
Income tax expense (benefit)	(14,122)	42,121
Net income (loss)	(155,101)	109,195
Net loss attributable to noncontrolling interests	(1,939)	(2,019)
Net income (loss) attributable to common stockholders of Cullinan	(153,162)	111,214
Comprehensive income (loss):
Net income (loss)	(155,101)	109,195
Unrealized gain (loss) on investments	2,472	(1,763)
Comprehensive income (loss)	(152,629)	107,432
Comprehensive loss attributable to noncontrolling interests	(1,939)	(2,019)
Comprehensive income (loss) attributable to Cullinan	$ (150,690)	$ 109,451
Net income (loss) per share attributable to common stockholders of Cullinan:
Basic	$ (3.69)	$ 2.46
Diluted	$ (3.69)	$ 2.38
Weighted-average shares used in computing net income (loss) per share attributable to common stockholders of Cullinan:
Basic	41,550	45,164
Diluted	41,550	46,640