Supplemental Inventory Information (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2012
Dec. 31, 2011
Inventory Disclosure [Abstract]    
Precious metals stated at LIFO cost $ 5,460 $ 4,447
Market value per ounce, Silver (in dollars per ounce) 30.20 27.95
Market value per ounce, Gold (in dollars per ounce) 1,675.40 1,565.80
Market value per ounce, Palladium (in dollars per ounce) 702.85 655.40