Revenue - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 28, 2019	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation Of Revenue [Line Items]
Revenue from collaboration agreement		$ 43,660,000	$ 38,505,000	$ 82,280,000	$ 76,947,000
Medicare Reimbursements
Disaggregation Of Revenue [Line Items]
Revenue from collaboration agreement		1,400,000	3,100,000	2,800,000	4,100,000
Medicare Reimbursements | Immune Medicine Service Revenue
Disaggregation Of Revenue [Line Items]
Revenue from collaboration agreement				200,000	100,000
Medicare Reimbursements | MRD Service Revenue
Disaggregation Of Revenue [Line Items]
Revenue from collaboration agreement				2,600,000	4,000,000.0
M R D Development Agreements | Maximum
Disaggregation Of Revenue [Line Items]
Additional milestone payment receivable		355,500,000		355,500,000
Genentech Collaboration Agreement
Disaggregation Of Revenue [Line Items]
Revenue from collaboration agreement		13,800,000	$ 17,200,000	26,000,000.0	$ 32,800,000
Non-refundable upfront payments received	$ 300,000,000.0			$ 300,000,000.0
Genentech Collaboration Agreement | Maximum
Disaggregation Of Revenue [Line Items]
Revenue recognition expected period				8 years
Genentech Collaboration Agreement | Maximum | Regulatory Milestones
Disaggregation Of Revenue [Line Items]
Expected revenue through milestone payments		75,000,000.0		$ 75,000,000.0
Genentech Collaboration Agreement | Maximum | Development Milestones
Disaggregation Of Revenue [Line Items]
Expected revenue through milestone payments		300,000,000.0		300,000,000.0
Genentech Collaboration Agreement | Maximum | Commercial Milestones
Disaggregation Of Revenue [Line Items]
Expected revenue through milestone payments		1,430,000,000.0		1,430,000,000.0
Genentech Collaboration Agreement | Minimum
Disaggregation Of Revenue [Line Items]
Expected revenue through milestone payments		$ 1,800,000,000		$ 1,800,000,000
Revenue recognition expected period				7 years