Sale of Stock, Aggregate Offering Price

No definition available.

Name:	mrtx_SaleofStockAggregateOfferingPrice
Namespace Prefix:	mrtx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Face amount or stated value per share of common stock.

+ References

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-Publisher FASB
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-SubTopic 10
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+ Details

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- Definition

Amount of cash inflow from exercise of option under share-based payment arrangement.

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Balance Type:	debit
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- Definition

Cash received on stock transaction after deduction of issuance costs.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The number of shares issued or sold by the subsidiary or equity method investee per stock transaction.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

+ References

No definition available.

+ Details

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Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of share options (or share units) exercised during the current period.

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- Details

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Namespace Prefix:
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Balance Type:
Period Type:

Shareholders' Equity - Narrative (Details) - USD ($)	1 Months Ended		3 Months Ended		6 Months Ended
Shareholders' Equity - Narrative (Details) - USD ($)	Oct. 31, 2020	Jan. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Jul. 02, 2020
Class of Stock [Line Items]
Stock issued in transaction (shares)	4,585,706	3,538,462
Sale price of common stock (USD per share)	$ 202.00	$ 97.50
Proceeds from sale of stock	$ 879,600,000	$ 324,000,000.0
Common stock, par value (USD per share)			$ 0.001		$ 0.001		$ 0.001
Stock issued pursuant to stock option exercises (shares)			224,129	323,789	537,032	820,310
Proceeds from stock options exercised			$ 6,600,000	$ 8,700,000	$ 16,500,000	$ 23,900,000
At the Market Facility
Class of Stock [Line Items]
Common stock, par value (USD per share)								$ 0.001
Aggregate offering price								$ 200,000,000.0