Derivative Instruments and Hedging Transactions - Summary of Hedging Activities Shows Precious Metal Commodity Inventory Position Net of Open Sale and Purchase Commitments (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Jun. 30, 2025
Derivatives, Fair Value [Line Items]
Inventories	$ 1,535,749	$ 1,279,545
Collectible coin inventory, held at lower of cost or net realizable value	(76,096)	(68,193)
Premium on metals position	(20,816)	(35,295)
Precious metal value not hedged	(96,912)	(103,488)
Commitments at market:
Open inventory purchase commitments	2,435,382	1,149,622
Open inventory sales commitments	(1,185,114)	(521,442)
Margin sales commitments	(43,459)	(27,446)
In-transit inventory no longer subject to market risk	(97,158)	(18,801)
Unhedgeable premiums on open commitment positions	15,760	10,345
Borrowed precious metals	(85,606)	(46,051)
Product financing arrangements	(504,593)	(484,733)
Advances on industrial metals	0	584
Commitments at market	535,212	62,078
Precious metal subject to price risk	1,974,049	1,238,135
Precious metal subject to derivative financial instruments:
Market value of derivative financial instruments	1,967,608	1,238,635
Net precious metals subject to commodity price risk	6,441	(500)
Precious metals forward contracts at market values
Precious metal subject to derivative financial instruments:
Market value of derivative financial instruments	1,255,256	927,990
Precious metals futures contracts at market values
Precious metal subject to derivative financial instruments:
Market value of derivative financial instruments	$ 712,352	$ 310,645