Joint Venture With General Motors - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Dec. 20, 2024	Mar. 31, 2025	Dec. 31, 2024	Apr. 01, 2025
Schedule of Equity Method Investments [Line Items]
Cash		$ 446,620	$ 593,885
Commited contribution				$ 191,600
Joint Venture with GM [Member]
Schedule of Equity Method Investments [Line Items]
Formation description		On October 15, 2024, the Company and GM entered into an investment agreement (“GM Investment Agreement”) to establish a joint venture (the “JV”) for the purpose of funding, developing, constructing and operating Thacker Pass as described in Note 4 to the Fiscal 2024 Annual Financial Statements. As of the closing of the JV on December 20, 2024
Closing date		Dec. 20, 2024
Ownership percentage	62.00%
Cash		$ 332,730	452,293
Joint Venture with GM [Member] | DOE loan [Member]
Schedule of Equity Method Investments [Line Items]
Outstanding borrowings and interest	$ 2,260,000	$ 0	$ 0
General Motors Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage	38.00%
Commited contribution				$ 100,000