Common Stock and Noncontrolling Interest in Subsidiaries - Additional Information (Details) - USD ($)			1 Months Ended									3 Months Ended			9 Months Ended
		May 28, 2020	Jul. 31, 2021	Jun. 30, 2021	Dec. 31, 2020	Nov. 30, 2020	Aug. 31, 2020	May 31, 2020	Apr. 30, 2020	Feb. 28, 2019	Dec. 31, 2018	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Common stock, shares authorized					34,900,878							150,000,000			150,000,000
Dividends declared												$ 0			$ 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							43,660,909			43,660,909
Losses attributed to noncontrolling interests												$ (909,000)		$ (1,456,000)	$ (223,000)	$ (6,899,000)	[1]
Aggregate purchase price	[2]															14,250,000
MICA
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares sold/issued					3,367,804
Shares price per share					$ 0.23
Aggregate purchase price					$ 800,000
Ownership interest percentage				45.00%	35.00%
MICA
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Equity at acquisition		$ 12,800,000
DFKZ and UFE Anti-dilution Shares
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Additional shares issued			0
Common Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Additional shares issued													13,685,000
License Agreement between Amber and Massachusetts Institute of Technology
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares sold/issued				153,229					400,132
License Agreement between Amber and Massachusetts Institute of Technology | Common Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Additional consideration received				$ 0					$ 0
Tubingen License Agreement | Common Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Additional shares issued					381,810
Tubingen License Agreement | Common Stock | DFKZ and UFE Anti-dilution Shares
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Additional consideration received					$ 0
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
Series A Preferred Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares issued				3,000,000
Gross proceeds				$ 3,000,000.0	$ 6,000,000.0		$ 9,000,000.0				$ 7,000,000.0
Shares sold/issued							9,000,000				7,000,000
Shares price per share											$ 1.00
Additional shares issued					6,000,000
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
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
Series A Preferred Stock | Maximum
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares sold/issued											11,000,000
Series A Preferred Stock | Maximum | Taiho Ventures, LLC
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Shares sold/issued										23,000,000
Series B Preferred Units
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Gross proceeds			$ 8,100,000
Additional shares issued			7,500,000
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
Series A Senior Preferred Stock | MICA
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Equity at acquisition		7,100,000
Junior Preferred and Common Stockholders | Noncontrolling Interest in Subsidiaries | MICA
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Equity at acquisition		$ 5,700,000
Cullinan Amber Corp | HLBV
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Losses attributed to noncontrolling interests												0		(200,000)		(200,000)
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
Gross proceeds									$ 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	0	0
Cullinan Florentine Corp | HLBV
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Losses attributed to noncontrolling interests												0		(300,000)	0	(300,000)
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
Cullinan Florentine Corp | Series A Preferred Stock
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Gross proceeds							$ 6,000,000.0
Sale of stock							6,000,000
Closing price per share							$ 1.00
Cullinan Florentine Corp | Series A Preferred Stock | Maximum
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Sale of stock							6,000,000
MICA | HLBV
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Losses attributed to noncontrolling interests												(300,000)			(800,000)	(5,100,000)
MICA | Maximum | HLBV
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Losses attributed to noncontrolling interests														(100,000)
Cullinan Pearl Corp | HLBV
Common Stock And Noncontrolling Interest In Subsidiaries [Line Items]
Losses attributed to noncontrolling interests												$ (600,000)		$ (900,000)	$ 700,000	$ (1,300,000)

[1] The shares and per share amounts for the nine months ended September 30, 2020 were derived from the unaudited 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 unaudited consolidated financial statements for additional details.

[2] Changes in equity activities for the nine months ended September 30, 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 unaudited consolidated financial statements for additional details.