Equity-Based Compensation - Additional Information (Details) $ / shares in Units, $ in Thousands			1 Months Ended		12 Months Ended
		Nov. 04, 2020 shares	Jan. 31, 2021 shares	Nov. 30, 2020 USD ($) Director $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 $ / shares	Dec. 31, 2018 $ / shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, par value | $ / shares					$ 0.0001	$ 0.0001
Common stock, shares issued					44,292,102	29,831,125
Equity-based compensation expense | $					$ 24,375	$ 14,910
Purchase of shares				2,254,231
Aggregate purchase price | $	[1]					145,450
Common stock exchange in excess fair value | $				$ 1,200
Common stock issued in exchange of units			320,228
Research and Development Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation expense | $					8,914	5,912
Share-based payment, modification expense | $				200
Equity-based compensation expense | $					400
General and Administrative Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation expense | $					$ 15,461	8,998
Share-based payment, modification expense | $				$ 100
Equity-based compensation expense | $						200
Pearl
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, par value | $ / shares								$ 0.0001
Amber and Florentine
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, par value | $ / shares							$ 0.0001
Unit Purchase Agreement with Cullinan Pearl
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase of shares				22,868
Shares price per share | $ / shares				$ 0.61
Common units transferred, Number of directors | Director				2
Aggregate subsidiary stock options, cancelled				93,000
Unit Purchase Agreement with Cullinan Pearl | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Aggregate purchase price | $				$ 100
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period					3 years
Restricted common units, related to exchange agreement with subsidiaries		320,228
Unrecognized compensation cost | $					$ 300	$ 700
Estimated weighted-average amortization period					1 year 5 months 23 days	2 years 4 months 28 days
Restricted Stock | Cullinan Amber Corp
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted common units, related to exchange agreement with subsidiaries				511,530
Restricted Stock | Cullinan Florentine Corp
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted common units, related to exchange agreement with subsidiaries				728,678
Restricted Stock | Cullinan Pearl Corp
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted common units, related to exchange agreement with subsidiaries				1,869,834
Restricted Stock | Tranche One
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting rights percent					25.00%
Restricted Stock | Tranche Two
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting rights percent					75.00%
Reorganization
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares issued			1,689,949
2016 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non- voting incentive units vesting percentage					25.00%
Non-voting incentive units remaining vesting percentage percentage					75.00%
Non-voting incentive units vesting period					3 years
Fair value of Non-voting incentive per units | $ / shares					$ 0.0001	$ 0.0001
Non-voting incentive units Issued						0
2020 Unit Option and Grant Plan | Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted common units, related to exchange agreement with subsidiaries				2,231,363
Exchange with Amber | Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted common units, related to exchange agreement with subsidiaries				368,974
Exchange with Florentine | Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted common units, related to exchange agreement with subsidiaries				513,656
Exchange with Pearl | Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted common units, related to exchange agreement with subsidiaries				1,348,733
2021 Stock Option and Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting rights percent					25.00%
Award vesting period					36 months
Unrecognized compensation cost | $					$ 75,800	$ 14,200
Common stock, shares reserved					12,546,386
Unrecognized compensation cost recognized weighted average period					3 years 1 month 24 days	2 years 8 months 4 days
Aggregate intrinsic value of options outstanding | $					$ 42,500	$ 63,100
Aggregate intrinsic value of options exercisable | $					$ 29,100	$ 28,600
Aggregate intrinsic value fair value per share | $ / shares					$ 15.43	$ 18.02
Annual dividend yield					0.00%
Weighted average fair value of options granted | $ / shares					$ 15.73	$ 6.19
Common stock issuable upon exercise of stock options, weighted average exercise price | $ / shares					$ 4.30
Split-adjusted restricted stock issued					320,228
Common stock issuable upon exercise of stock options					4,616,187
Increase in number of shares reserved and available for issuance percentage					5.00%
2021 Stock Option and Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Term of options					10 years
2021 Stock Option and Incentive Plan | Research and Development Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation expense | $					$ 8,700	$ 5,600
2021 Stock Option and Incentive Plan | General and Administrative Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation expense | $					$ 15,200	$ 8,800
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares issued					12,977
Common stock, shares reserved					416,665
Increase in number of shares reserved and available for issuance percentage					1.00%
Increase in number of shares reserved and available for issuance					833,330
ESPP | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation expense | $					$ 100

[1] 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.