Cullinan-MICA Asset Acquisition - Additional Information (Details)			1 Months Ended	12 Months Ended
	Dec. 31, 2021 shares	May 28, 2020 USD ($) shares	Jun. 30, 2021 USD ($) shares	Dec. 31, 2021 USD ($) Milestone shares	Dec. 31, 2020 USD ($) shares	May 31, 2020 shares
Schedule Of Asset Acquisition [Line Items]
Common stock, shares authorized	150,000,000			150,000,000	34,900,878
Common stock, shares outstanding	44,292,102			44,292,102	29,831,125
Voting agreement description				Voting Agreement dated May 28, 2020, among the Company and other stockholders of MICA, MICA increased the size of its board of directors from four to five directors, of which three directors are designated by the Company.
Acquired in-process research and development assets | $					$ 6,447,000
MICA
Schedule Of Asset Acquisition [Line Items]
Number of share authorized for issuance		72,890,797
Common stock, shares authorized		39,000,000
Preferred stock shares authorized		33,890,797
Number of shares outstanding						22,829,406
Common stock, shares outstanding						602,784
MICA Equity Plan
Schedule Of Asset Acquisition [Line Items]
Common stock, shares reserved						2,034,457
MICAs Directors and Officers, as well as Former Employees of PDI Therapeutics | MICA Equity Plan
Schedule Of Asset Acquisition [Line Items]
Common stock, shares reserved						1,826,402
Series A Senior Preferred Stock | MICA
Schedule Of Asset Acquisition [Line Items]
Preferred stock shares authorized		19,786,914
Ownership percentage in outstanding shares	88.50%			88.50%
Series A Senior Preferred Stock | MICA Board Authorized First Additional Closing
Schedule Of Asset Acquisition [Line Items]
Number of share purchased as part of asset acquisition			5,385,787
Share purchased price as part of asset acquisition | $			$ 7,100,000
Ownership percentage increased in outstanding shares	45.00%		45.00%
Series A Senior Preferred Stock | Certain Existing Shareholders | MICA Board Authorized First Additional Closing
Schedule Of Asset Acquisition [Line Items]
Number of share purchased as part of asset acquisition			702,495
Share purchased price as part of asset acquisition | $			$ 900,000
Series A Junior Preferred Stock | MICA
Schedule Of Asset Acquisition [Line Items]
Preferred stock shares authorized		1,999,998
Preferred stock shares outstanding						6,088,282
Series A Junior Preferred Stock | Cullinan Oncology, LLC
Schedule Of Asset Acquisition [Line Items]
Preferred stock shares outstanding						5,385,787
Series A-1 Junior Preferred Stock | MICA
Schedule Of Asset Acquisition [Line Items]
Preferred stock shares authorized		652,371
Series A-2 Junior Preferred Stock | MICA
Schedule Of Asset Acquisition [Line Items]
Preferred stock shares authorized		11,451,514
Series A, A-1 and A2 Junior Preferred Stock | MICA
Schedule Of Asset Acquisition [Line Items]
Preferred stock shares outstanding						14,103,883
Fully Diluted Shares | MICA
Schedule Of Asset Acquisition [Line Items]
Ownership percentage in outstanding shares	24.00%			24.00%
Ownership percentage can increase with subsequent closings	54.00%			54.00%
Research and Development Expense
Schedule Of Asset Acquisition [Line Items]
Acquired in-process research and development assets | $					$ 6,400,000
Series A Senior Preferred Stock Purchase Agreement
Schedule Of Asset Acquisition [Line Items]
Number of additional closings | Milestone				2
Series A Senior Preferred Stock Purchase Agreement | Series A Senior Preferred Stock | PDI Therapeutics, Inc.
Schedule Of Asset Acquisition [Line Items]
Number of share purchased as part of asset acquisition		5,385,787
Share purchased price as part of asset acquisition | $		$ 7,100,000
Series A Senior Preferred Stock Purchase Agreement | Series A Senior Preferred Stock | Certain Existing PDI Therapeutics Shareholders | PDI Therapeutics, Inc.
Schedule Of Asset Acquisition [Line Items]
Number of share purchased as part of asset acquisition		702,495
Share purchased price as part of asset acquisition | $		$ 900,000
Series A Senior Preferred Stock Purchase Agreement | Maximum
Schedule Of Asset Acquisition [Line Items]
Proceeds from preferred stock | $				$ 26,000,000.0