Debt conversion, converted instrument, of pre funded warrants.

No definition available.

Name:	kpti_DebtConversionConvertedInstrumentOfPreFundedWarrants
Namespace Prefix:	kpti_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The value of the financial instrument(s) that the original debt is being converted into in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482913/230-10-50-3

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The number of shares issued in exchange for the original debt being converted in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or payments in the period.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The price per share of the conversion feature embedded in the debt instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-5

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 55
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482949/835-30-55-8

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
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Reference 4: http://www.xbrl.org/2003/role/exampleRef
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-Topic 835
-SubTopic 30
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482925/835-30-45-2

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The average effective interest rate during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477657/942-210-S45-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 942
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 942
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-Name Accounting Standards Codification
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-Publisher FASB
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
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-URI https://asc.fasb.org/1943274/2147482925/835-30-45-2

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 830
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481674/830-30-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 855
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-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483399/855-10-50-2

+ Details

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Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=us-gaap_ConvertibleDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=kpti_NewTwoThousandTwentyNineNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Subsequent Event - 2029 Notes - Additional Information (Detail) - USD ($)			6 Months Ended
	Oct. 07, 2025	May 13, 2024	Jun. 30, 2026	Dec. 31, 2025
2029 Notes [Member]
Subsequent Event [Line Items]
Aggregate principal amount	$ 101,000,000	$ 5,000,000	$ 0
Notes, interest rate			6.00%
2029 Notes [Member] \| Common Stock [Member]
Subsequent Event [Line Items]
Notes converted in to common stock, amount	2,024,344
Pre-funded warrants to common stock	552,164
2029 Notes [Member] \| Convertible Note Offering [Member]
Subsequent Event [Line Items]
Notes converted in to common stock, amount			29.6296
Notes, conversion price per share			$ 33.75
Notes converted in to common stock, shares	$ 15,000,000	$ 1,000
New 2029 Notes [Member]
Subsequent Event [Line Items]
Aggregate principal amount	$ 103,500,000		$ 107,974,000	$ 105,598,000
Notes converted in to common stock, amount			85.1374
Notes converted in to common stock, shares			$ 1,000
New 2029 Notes [Member] \| Convertible Note Offering [Member]
Subsequent Event [Line Items]
Notes converted in to common stock, amount			44.4444
Notes, conversion price per share			$ 22.5
Notes converted in to common stock, shares			$ 1,000