Commitments and Contingencies - Contract Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Business Acquisition [Line Items]
Revenue Recognized	$ 25,468	$ 15,887	$ 16,226
Franco-Nevada
Business Acquisition [Line Items]
Opening Balance	7,411	8,150	9,376
Revenue Recognized	(469)	(739)	(1,226)
Closing Balance	6,942	7,411	8,150
Kensington
Business Acquisition [Line Items]
Opening Balance	25,016	15,016	15,003
Additions	130,066	36,020	30,013
Revenue Recognized	(100,000)	(26,020)	(30,000)
Closing Balance	55,082	$ 25,016	$ 15,016
Kensington | December 2023 Prepayment
Business Acquisition [Line Items]
Closing Balance	25,000
Kensington | June 2023 Prepayment
Business Acquisition [Line Items]
Closing Balance	25,000
Wharf | September 2023 Prepayment
Business Acquisition [Line Items]
Closing Balance	12,500
Wharf | December 2023 Prepayment
Business Acquisition [Line Items]
Closing Balance	12,500
Rochester | September 2023 Prepayment
Business Acquisition [Line Items]
Closing Balance	17,500
Rochester | December 2023 Prepayment
Business Acquisition [Line Items]
Closing Balance	17,500
Rochester | June 2023 Prepayment
Business Acquisition [Line Items]
Closing Balance	$ 10,000