Balance Sheet Items - Summary of Prepaid and Other Current Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid research and development expenses	$ 9,521	$ 8,216
Prepaid insurance	1,788	830
Other prepaid expenses and other assets	3,804	4,367
Total prepaid expenses and other current assets	$ 15,113	$ 13,413

Prepaid Research and Development Expenses.

No definition available.

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Namespace Prefix:	dawn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of asset related to consideration paid in advance for other costs that provide economic benefits within a future period of one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(7))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 340
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483032/340-10-45-1

+ Details

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

- Definition

Amount of asset related to consideration paid in advance for costs that provide economic benefits in future periods, and amount of other assets that are expected to be realized or consumed within one year or the normal operating cycle, if longer.

+ References

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount of asset related to consideration paid in advance for insurance that provides economic benefits within a future period of one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (g)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483467/210-10-45-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 340
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483032/340-10-45-1

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 340
-SubTopic 10
-Name Accounting Standards Codification
-Section 05
-Paragraph 5
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482955/340-10-05-5

+ Details

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