Acquisitions (Details) $ / shares in Units, $ in Thousands, € in Millions											1 Months Ended			3 Months Ended				9 Months Ended		12 Months Ended
	Jul. 21, 2025 USD ($)	Apr. 01, 2025 USD ($)	Jul. 03, 2024 USD ($)	Jul. 03, 2024 EUR (€)	Jul. 02, 2024 USD ($)	Jun. 27, 2024 EUR (€)	Jun. 18, 2024 USD ($)	Jun. 15, 2024 USD ($) LicensedAsset shares	Jun. 14, 2024	Jan. 08, 2024 USD ($)	May 31, 2025 USD ($)	Jan. 31, 2025 USD ($) $ / shares shares	Aug. 31, 2024 USD ($)	Sep. 30, 2025 USD ($) $ / shares shares	Mar. 31, 2025 USD ($)	Sep. 30, 2024 USD ($) $ / shares shares	Mar. 31, 2024 USD ($)	Sep. 30, 2025 USD ($) $ / shares shares	Sep. 30, 2024 USD ($) $ / shares shares	Dec. 31, 2024 USD ($) shares	Mar. 06, 2024 $ / shares shares	Jan. 22, 2024 $ / shares shares
Asset Acquisition [Line Items]
Additional cash payment required														$ 97,824				$ 97,824
Acquisition of exclusive license option																		0	$ 28,000
Research and development														$ 48,025		$ 24,148		$ 129,828	$ 132,773
Radiopharm Theranostics Limited
Asset Acquisition [Line Items]
Shares owned (in shares) | shares												133,333,333		282,958,513		149,625,180		282,958,513	149,625,180	149,625,180
Percentage of shares outstanding																		12.00%
Share price (in dollars per share) | $ / shares												$ 0.04		$ 0.02		$ 0.03		$ 0.02	$ 0.03
Purchase amount in investment in equity securities												$ 5,000				$ 5,000
Radiopharm Theranostics Limited | Maximum [Member]
Asset Acquisition [Line Items]
Equity Method Investment Shares Outstanding | $ / shares																		$ 20
Agreement with Perspective Therapeutics, Inc
Asset Acquisition [Line Items]
Disposal group consideration										$ 8,000
Perspective Therapeutics, Inc
Asset Acquisition [Line Items]
Subsidiary, ownership percentage, noncontrolling owner																					19.90%
Research and development																	$ 28,000
Shares owned (in shares) | shares								11,677,339						11,677,339				11,677,339
Conversion ratio									0.1
Share price (in dollars per share) | $ / shares														$ 3.43				$ 3.43
Perspective Therapeutics, Inc | Licenses
Asset Acquisition [Line Items]
Acquisition of exclusive license option										$ 28,000
Perspective Therapeutics, Inc, Fully Diluted Basis
Asset Acquisition [Line Items]
Subsidiary, ownership percentage, noncontrolling owner																					17.35%
Perspective Common Stock
Asset Acquisition [Line Items]
Shares acquired (in shares) | shares														11,677,339				11,677,339			60,431,039	56,342,355
Percentage of acquired interest														16.00%				16.00%				11.39%
Share price (in dollars per share) | $ / shares																					$ 0.95	$ 0.37
Evergreen Theragnostics
Asset Acquisition [Line Items]
Payments to acquire businesses		$ 276,424
Additional cash payment required		25,000
Acquisition and integration related costs														$ 5,800				$ 23,300
Payment of transaction expenses		11,600
Nonrecurring post combination expense																		7,500
Component of consideration transferred		6,100
Pre existing debt		4,300
Additional Milestone Payments | Evergreen Theragnostics
Asset Acquisition [Line Items]
Additional cash payment required		$ 727,500
Regulatory Milestones | RM2 Sublicense Agreement [Member]
Asset Acquisition [Line Items]
Payment for acquisitions | €						€ 5.0
Radiopharm Theranostics Limited
Asset Acquisition [Line Items]
Research and development																				$ 2,000
Payment for acquisitions								$ 2,000
Asset acquisition, additional milestone payments								$ 20,000
Number of licensed asset acquired | LicensedAsset								2
Radiopharm Theranostics Limited | Sales Milestones
Asset Acquisition [Line Items]
Asset acquisition, additional milestone payments								$ 6,500
Meilleur Technologies, Inc
Asset Acquisition [Line Items]
Payment for acquisitions							$ 32,900						$ 10,000
Asset acquisition, additional milestone payments							43,000
Meilleur Technologies, Inc | Research Revenue Milestones
Asset Acquisition [Line Items]
Asset acquisition, additional milestone payments							$ 4,000
Life Molecular Imaging, RM2 Technology
Asset Acquisition [Line Items]
Research and development															$ 5,400				$ 36,000
Payment for acquisitions			$ 35,000		$ 1,000
Contingent regulatory and development milestones | €				€ 45.0
Life Molecular Imaging, RM2 Technology | Sales Milestones
Asset Acquisition [Line Items]
Asset acquisition, additional milestone payments | €				280.0
Life Molecular Imaging, RM2 Technology | Regulatory Milestones
Asset Acquisition [Line Items]
Asset acquisition, additional milestone payments | €				€ 127.5
AstraZeneca
Asset Acquisition [Line Items]
Non-refundable upfront payment to adjust the future royalty obligations											$ 10,000
Life Molecular Imaging Ltd
Asset Acquisition [Line Items]
Acquisition and integration related costs														$ 22,200				$ 27,600
Payment for acquisitions	$ 355,200
Asset acquisition, additional milestone payments	$ 400,000