Inventories, Net - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Bank of Nova Scotia \| Consignment Agreement \| Silver
Inventory [Line Items]
Merchandise under consignment	$ 24,735	$ 6,880

Gross amount of inventory owned by the entity but in the hands of a customer, typically a reseller.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(6)(a))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_OtherInventoryMaterialsSuppliesAndMerchandiseUnderConsignment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant