Label	Element	Value
Development Milestone Payments [Member] | Pfizer Discovery and Collaboration Agreement [Member]
Collaborative Arrangement, Research and Development Arrangement, Discovery and Collaboration Agreement, Compensation Expected to be Paid	mrtx_CollaborativeArrangementResearchAndDevelopmentArrangementDiscoveryAndCollaborationAgreementCompensationExpectedToBePaid	$ 9,300,000
Collaborative Arrangement, Research and Development Arrangement, Discovery and Collaboration Agreement, Milestone Payments Paid	mrtx_CollaborativeArrangementResearchAndDevelopmentArrangementDiscoveryAndCollaborationAgreementMilestonePaymentsPaid	9,500,000
Sales Milestone Payments [Member] | Pfizer Discovery and Collaboration Agreement [Member]
Collaborative Arrangement, Research and Development Arrangement, Discovery and Collaboration Agreement, Compensation Expected to be Paid	mrtx_CollaborativeArrangementResearchAndDevelopmentArrangementDiscoveryAndCollaborationAgreementCompensationExpectedToBePaid	$ 337,000,000.0