License and Collaboration Agreements - Narrative (Details) - USD ($)				1 Months Ended	12 Months Ended
	May 28, 2021	Aug. 03, 2020	Jan. 07, 2018	Oct. 31, 2014	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Expenses related to collaboration agreement					$ 508,594,000	$ 299,349,000	$ 182,866,000
Income tax expense					3,299,000	0	0
Milestone Payments
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Expenses related to collaboration agreement						4,800,000
BeiGene Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Up-front fee received			$ 10,000,000
Revenue from performance obligation expected to be earned			$ 123,000,000
Termination of contract, period after first commercial sale of product			10 years
Period required for notice of termination of contract			60 days
Revenue from performance obligation earned							500,000
BeiGene Agreement | Licenses of Intellectual Property
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue from performance obligation earned								$ 9,500,000
BeiGene Agreement | Manufacturing Supply Services
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue from performance obligation earned						1,800,000	300,000
Revenue recognized							(3,300,000)
Cost sharing receivable					300,000	1,300,000
Revenue from Contract with Customer, Including Assessed Tax					400,000	2,000,000
Contract with Customer, Liability, Revenue Recognized						200,000	3,000,000
BeiGene Agreement | Milestone Payments
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue recognized						0	0
Contract with Customer, Milestone Payments Receivable					5,000,000
BeiGene Agreement | Royalties
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue					0	0	0
Pfizer Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Termination of contract, period after first commercial sale of product				10 years
Period required for notice of termination of contract				60 days
Expenses related to collaboration agreement							7,000,000
Pfizer Agreement | adagrasib
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Expenses related to collaboration agreement					5,000,000
Pfizer Agreement | Research and Development Services
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Expenses related to collaboration agreement							$ 6,000,000
Pfizer Agreement | Milestone Payments | adagrasib
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Expenses related to collaboration agreement						3,000,000
Pfizer Agreement | Milestone Payments | MRTX1133
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Expenses related to collaboration agreement						300,000
Pfizer Agreement | Research and Development Services
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Expenses related to collaboration agreement						$ 1,500,000
ORIC Pharmaceuticals Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Stock received as part of stock issuance and license agreements (shares)		588,235
License agreement, period of transfer restrictions		18 months
License agreement, period of agreement after first commercial sale		10 years
ORIC Pharmaceuticals Agreement | Level 3
Research and Development Arrangement, Contract to Perform for Others [Line Items]
License agreement, transaction price		$ 11,400,000
Zai Collaboration and License Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaboration Arrangement, Research and Development Arrangement, Up-Front Fee Received	$ 65,000,000
Collaborative Arrangement, Research and Development Arrangement, Discovery and Collaboration Agreement, Termination of Contract, Period after First Commercial Sale of Product	10 years
Collaboration Arrangement, Research and Development Arrangement, Contract to Perform for Others, Period Required for Notice of Termination of Contract	12 months
Collaboration Arrangement, Research and Development Arrangement, Transaction Price	$ 66,600,000
Zai Collaboration and License Agreement | Licenses of Intellectual Property
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue from Contract with Customer, Including Assessed Tax					66,600,000
Income tax expense					3,300,000
Zai Collaboration and License Agreement | Manufacturing Supply Services
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue from Contract with Customer, Including Assessed Tax					0
Zai Collaboration and License Agreement | Sales Milestone Payments
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaboration Arrangement, Research and Development Arrangement, Contract to Perform for Others, Compensation Expected to be Earned	180,000,000
Zai Collaboration and License Agreement | Royalties
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue					$ 0
Zai Collaboration and License Agreement | Development and Regulatory-Based Milestone Payments
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaboration Arrangement, Research and Development Arrangement, Contract to Perform for Others, Compensation Expected to be Earned	$ 93,000,000