Nature of Business and Basis of Presentation - Additional Information (Details) $ in Millions	Dec. 31, 2023 USD ($)
Nature Of Business And Basis Of Presentation [Line Items]
Cash equivalents short term investments and interest recivable	$ 468.3

Cash Equivalents Short Term Investments And Interest recivable

No definition available.

Name:	cgem_CashEquivalentsShortTermInvestmentsAndInterestRecivable
Namespace Prefix:	cgem_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant