License and Collaboration Agreements (Details) - USD ($) $ in Thousands	1 Months Ended					3 Months Ended			9 Months Ended		105 Months Ended
	Nov. 30, 2024	Oct. 31, 2024	Apr. 30, 2024	Mar. 31, 2024	Jan. 31, 2024	Sep. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Mar. 31, 2025
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
License and collaboration revenue						$ 4,712		$ 4,675	$ 38,579	$ 263,795
Revenue from Contract with Customer, Product and Service [Extensible Enumeration]						License And Service		License And Service	License And Service	License And Service
Recognized revenue from deferred revenue contract liability						$ 4,700		$ 4,700	$ 14,900	$ 0
Contract with customer, deferred revenue contract liability								36,200		36,200
Phase 3 clinical trial for a second-generation compound for any indication
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Increase in milestone payment	$ 50,000
Milestone payment receivable	165,000	$ 115,000
Janssen \| Restated Agreement \| Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of royalties on net product sales									6.00%
Janssen \| Restated Agreement \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of royalties on net product sales									10.00%
Janssen \| License and collaboration agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
License and collaboration revenue							$ 165,000
Proceeds from Milestone Payments											$ 337,500
Janssen \| License and collaboration agreement \| Food And Drug administration approval of New Drug Application in any indication.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upcoming potential development milestones						50,000			$ 50,000		50,000
Janssen \| License and collaboration agreement \| Acceptance of New Drug Application filed by Food And Drug Administration approval for second indication
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upcoming potential development milestones						25,000			25,000		25,000
Janssen \| License and collaboration agreement \| Food And Drug Administration approval of New Drug Application for second indication
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upcoming potential development milestones						45,000			45,000		45,000
Janssen \| License and collaboration agreement \| Dosing of the 3rd patient in a Phase 3 clinical trial for a second-generation compound for any indication
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upcoming potential development milestones						35,000			35,000		35,000
Janssen \| License and collaboration agreement \| Acceptance of New Drug Application filed by Food And Drug Administration approval for any indication
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Elimination of previously due milestone payment	35,000
Janssen \| License and collaboration agreement \| Phase 3 clinical trial for a second-generation compound for any indication
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upcoming potential development milestones						50,000			50,000		50,000
Janssen \| License and collaboration agreement \| Dosing of third patient in first phase3 clinical trial for second indication
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Elimination of previously due milestone payment	$ 15,000
Takeda Pharmaceuticals \| License And Service
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Profit (loss) share on U.S. profits and losses			50.00%
Takeda Pharmaceuticals \| Development Services
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment					$ 45,900
Revenue recognized										9,700
Takeda Pharmaceuticals \| License and collaboration agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Non-refundable upfront payment			$ 300,000
Final transaction price					300,000							$ 325,000
Revenue recognized				$ 254,100		4,700		$ 4,700	38,600	$ 263,800
Takeda Pharmaceuticals \| License and collaboration agreement \| Phase 3 clinical trial for rusfertide in PV
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
License and collaboration revenue									21,300
Milestone payment						25,000			25,000		25,000
Upcoming potential development and regulatory milestone payments receivable						25,000			25,000		25,000	25,000
Takeda Pharmaceuticals \| License and collaboration agreement \| Food And Drug Administration approval Of new drug application for rusfertide in PV
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upcoming potential development and regulatory milestone payments receivable					50,000
Takeda Pharmaceuticals \| License and collaboration agreement \| Food And Drug Administration approval Of new drug application for rusfertide in PV \| Exercise of full opt-out right
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upcoming potential development and regulatory milestone payments receivable					75,000
Takeda Pharmaceuticals \| License and collaboration agreement \| First regulatory approval in three European countries
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upcoming potential development and regulatory milestone payments receivable					15,000
Takeda Pharmaceuticals \| License and collaboration agreement \| First regulatory approval in japan
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upcoming potential development and regulatory milestone payments receivable					$ 10,000
Takeda Pharmaceuticals \| License and collaboration agreement \| Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of royalties on ex-U.S. net sales			10.00%		14.00%
Takeda Pharmaceuticals \| License and collaboration agreement \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaborative arrangement, milestone payment, eligible to receive			$ 305,000
Additional payment eligible to receive from a collaborative arrangement					$ 200,000
Percentage of royalties on ex-U.S. net sales			17.00%		29.00%
Takeda Pharmaceuticals \| License and collaboration agreement \| Maximum \| Exercise of full opt-out right
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaborative arrangement, milestone payment, eligible to receive					$ 975,000
Takeda Pharmaceuticals \| License and collaboration agreement \| Maximum \| Exercise of full opt out right during the initial opt out period
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaborative arrangement, milestone payment, eligible to receive					200,000
Takeda Pharmaceuticals \| License and collaboration agreement \| License and Maintenance
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment					$ 254,100
Milestone payments allocated to performance obligations												21,300
Takeda Pharmaceuticals \| License and collaboration agreement \| Development Services
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Final transaction price						$ 17,000			17,000		$ 17,000
License and collaboration revenue									$ 17,300
Milestone payments allocated to performance obligations												$ 3,700

Protagonist Therapeutics, Inc 10-Q