SUBSEQUENT EVENTS	12 Months Ended
Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Event On January 7, 2018, the Company and BeiGene, Ltd. (“BeiGene”) entered into a Collaboration and License Agreement (the “Agreement”), under which the Company and BeiGene agreed to collaboratively develop sitravatinib in Asia (excluding Japan and certain other countries), Australia and New Zealand (the “Licensed Territory”). BeiGene is considered a related party as the Company and BeiGene have a common investor. Under the Agreement, Mirati granted BeiGene an exclusive license to develop, manufacture and commercialize sitravatinib in the Licensed Territory, with Mirati retaining exclusive rights for the development, manufacturing and commercialization of sitravatinib outside the Licensed Territory. As consideration for the rights granted to BeiGene under the Agreement, BeiGene agreed to pay to Mirati an upfront fee of $10.0 million. BeiGene is also required to make milestone payments to Mirati of up to an aggregate of $123.0 million upon the first achievement of specified clinical, regulatory and sales milestones. The Agreement additionally provides that BeiGene is obligated to pay to Mirati royalties at tiered percentage rates ranging from mid-single digits to twenty percent on annual net sales of licensed products in the Licensed Territory, subject to reduction under specified circumstances. The Agreement will terminate upon the expiration of the last royalty term for the licensed products, which is the latest of (i) the date of expiration of the last valid patent claim related to the licensed products under the Agreement, (ii) 10 years after the first commercial sale of a licensed product and (iii) the expiration of any regulatory exclusivity as to a licensed product. BeiGene may terminate the Agreement at any time by providing 60 days’ prior written notice to Mirati. Either party may terminate the Agreement upon a material breach by the other party that remains uncured following 60 days after the date of written notice of such breach or upon certain bankruptcy events. In addition, Mirati may terminate the Agreement upon written notice to BeiGene under specified circumstances if BeiGene challenges the licensed patent rights.

Subsequent Event

On January 7, 2018, the Company and BeiGene, Ltd. (“BeiGene”) entered into a Collaboration and License Agreement (the “Agreement”), under which the Company and BeiGene agreed to collaboratively develop sitravatinib in Asia (excluding Japan and certain other countries), Australia and New Zealand (the “Licensed Territory”). BeiGene is considered a related party as the Company and BeiGene have a common investor. Under the Agreement, Mirati granted BeiGene an exclusive license to develop, manufacture and commercialize sitravatinib in the Licensed Territory, with Mirati retaining exclusive rights for the development, manufacturing and commercialization of sitravatinib outside the Licensed Territory.

As consideration for the rights granted to BeiGene under the Agreement, BeiGene agreed to pay to Mirati an upfront fee of $10.0 million. BeiGene is also required to make milestone payments to Mirati of up to an aggregate of $123.0 million upon the first achievement of specified clinical, regulatory and sales milestones. The Agreement additionally provides that BeiGene is obligated to pay to Mirati royalties at tiered percentage rates ranging from mid-single digits to twenty percent on annual net sales of licensed products in the Licensed Territory, subject to reduction under specified circumstances.

The Agreement will terminate upon the expiration of the last royalty term for the licensed products, which is the latest of (i) the date of expiration of the last valid patent claim related to the licensed products under the Agreement, (ii) 10 years after the first commercial sale of a licensed product and (iii) the expiration of any regulatory exclusivity as to a licensed product. BeiGene may terminate the Agreement at any time by providing 60 days’ prior written notice to Mirati. Either party may terminate the Agreement upon a material breach by the other party that remains uncured following 60 days after the date of written notice of such breach or upon certain bankruptcy events. In addition, Mirati may terminate the Agreement upon written notice to BeiGene under specified circumstances if BeiGene challenges the licensed patent rights.