Stockholders' Equity - Schedule of Development Subsidiaries and Their Product Candidates (Details) - Subsidiaries [Member]	Dec. 31, 2025	Dec. 31, 2024
Cullinan M I C A Corp [Member]
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Subsidiary, Ownership Percentage	99.00%	99.00%
Cullinan Florentine Corp [Member]
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Subsidiary, Ownership Percentage	98.00%	98.00%
Cullinan Amber Corp [Member]
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Subsidiary, Ownership Percentage	96.00%	96.00%