Common Stock and Noncontrolling Interest in Subsidiaries - Additional Information (Details) - USD ($)			1 Months Ended									12 Months Ended
		May 28, 2020	Jul. 31, 2021	Jun. 30, 2021	Jan. 31, 2021	Dec. 31, 2020	Nov. 30, 2020	Aug. 31, 2020	May 31, 2020	Apr. 30, 2020	Feb. 28, 2019	Dec. 31, 2021	Dec. 31, 2020		Dec. 31, 2018
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Common stock, shares authorized						34,900,878						150,000,000	34,900,878
Dividends declared												$ 0
Common stock, voting rights												Each share of common stock entitles the holder to one vote and to receive dividends when and if declared by the board of directors of the Company.
Shares sold/issued						29,831,125						44,292,102	29,831,125
Losses attributed to noncontrolling interests												$ (1,915,000)	$ (7,659,000)	[1]
Aggregate purchase price	[2]												145,450,000
Purchase of shares							2,254,231
Common Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Additional shares issued												13,685,000
Series A Preferred Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares sold/issued											9,000,000
Shares price per share											$ 1.00
Cullinan Amber Corp | HLBV
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Losses attributed to noncontrolling interests													200,000
Cullinan Amber Corp | MIT License Agreement between Amber and MIT
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares sold/issued				153,229						400,132
Cullinan Amber Corp | MIT License Agreement between Amber and MIT | Common Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Additional consideration received				$ 0						$ 0
Cullinan Amber Corp | Maximum | HLBV
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Losses attributed to noncontrolling interests												$ 100,000
Cullinan Amber Corp | Series A Preferred Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares issued				3,000,000						3,000,000
Gross proceeds				$ 3,000,000.0						$ 3,000,000.0
Closing price per share										$ 1.00
Cullinan Amber Corp | Series A Preferred Stock | Maximum
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Sale of stock										9,000,000
Cullinan Apollo Corp
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Losses attributed to noncontrolling interests												0	0
Cullinan Apollo Corp | Series A Preferred Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Gross proceeds															$ 7,000,000.0
Shares sold/issued															7,000,000
Shares price per share															$ 1.00
Cullinan Apollo Corp | Series A Preferred Stock | Maximum
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares sold/issued															11,000,000
Cullinan Florentine Corp | DFKZ and UFE Anti-dilution Shares
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Additional shares issued			0
Cullinan Florentine Corp | HLBV
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Losses attributed to noncontrolling interests												0	500,000
Cullinan Florentine Corp | Tubingen License Agreement
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares sold/issued								725,118
Cullinan Florentine Corp | Tubingen License Agreement | Common Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Additional consideration received								$ 0
Additional shares issued						381,810
Cullinan Florentine Corp | Tubingen License Agreement | Common Stock | DFKZ and UFE Anti-dilution Shares
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Additional consideration received						$ 0
Cullinan Florentine Corp | Series A Preferred Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Gross proceeds						$ 6,000,000.0		$ 6,000,000.0
Sale of stock								6,000,000
Closing price per share								$ 1.00
Additional shares issued						6,000,000
Cullinan Florentine Corp | Series A Preferred Stock | Maximum
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Sale of stock								6,000,000
Cullinan Florentine Corp | Series B Preferred Units
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Gross proceeds			$ 8,100,000
Additional shares issued			7,500,000
Cullinan Pearl Corp | HLBV
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Losses attributed to noncontrolling interests												700,000	$ 1,600,000
Cullinan Pearl Corp | Subscription Agreement between Company and Pearl | Common Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares price per share							$ 0.44
Aggregate purchase price							$ 1,200,000
Purchase of shares							2,730,227
Cullinan Pearl Corp | Series A Preferred Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Gross proceeds								$ 9,000,000.0
Shares sold/issued								9,000,000
Cullinan Pearl Corp | Series A Preferred Stock | Taiho Ventures, LLC
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Gross proceeds											$ 14,000,000.0
Shares sold/issued											14,000,000
Shares price per share											$ 1.00
Cullinan Pearl Corp | Series A Preferred Stock | Taiho License Agreement
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares sold/issued								1,206,000			1,860,000
Additional consideration received								$ 0
Aggregate purchase price											$ 0
Cullinan Pearl Corp | Series A Preferred Stock | Maximum | Taiho Ventures, LLC
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares sold/issued											23,000,000
MICA
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares sold/issued						3,367,804							3,367,804
Shares price per share						$ 0.23							$ 0.23
Equity at acquisition		$ 12,800,000
Aggregate purchase price						$ 800,000
Ownership interest percentage				45.00%		35.00%
MICA | HLBV
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Losses attributed to noncontrolling interests					$ 1,100,000							$ 5,400,000
MICA | Series A Senior Preferred Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares issued									6,088,282
Shares price per share									$ 1.31
Number of share purchased as part of asset acquisition									5,385,787
Equity at acquisition		7,100,000
MICA | Junior Preferred and Common Stockholders | Noncontrolling Interests in Subsidiaries
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Equity at acquisition		$ 5,700,000

[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] Changes in equity activities for the year ended December 31, 2020 were retroactively adjusted, including shares and per share amounts, as a result of the Reorganization and Reverse Stock Split. See Note 3 to the consolidated financial statements for additional details.