Inventories, Net Supplemental Inventory Information (Details) $ in Thousands	Jun. 30, 2015 USD ($) $ / oz	Dec. 31, 2014 USD ($) $ / oz
Inventory Disclosure [Abstract]
Precious metals stated at LIFO cost | $	$ 7,909	$ 4,839
Precious metals stated under non-LIFO cost methods, primarily at fair value | $	$ 12,431	$ 12,165
Market value per ounce, Silver (in dollars per ounce)	15.79	15.75
Market value per ounce, Gold (in dollars per ounce)	1,170.50	1,199.25
Market value per ounce, Palladium (in dollars per ounce)	676.00	798.00