Inventories (Supplemental Information) (Details) $ in Thousands	Dec. 31, 2016 USD ($) $ / oz	Dec. 31, 2015 USD ($) $ / oz
Inventory Disclosure [Abstract]
Precious metals stated at LIFO cost | $	$ 4,977	$ 3,506
Precious metals stated under non-LIFO cost methods, primarily at fair value | $	$ 9,339	$ 9,619
Market value per ounce:
Silver (in dollars per ounce)	16.05	13.86
Gold (in dollars per ounce)	1,159.10	1,062.25
Palladium (in dollars per ounce)	676.00	547.00