Derivative Instruments (Details 1) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012
Futures and Forwards Contracts [Member] | Gold, Ounces
Derivative [Line Items]
Forward and future contracts	$ 2.2
Futures and Forwards Contracts [Member] | Silver, Ounces
Derivative [Line Items]
Forward and future contracts	2.7
Forward Contracts [Member]
Derivative [Line Items]
Forward and future contracts	$ 3.1
Not Designated as Hedging Instrument [Member] | Futures and Forwards Contracts [Member] | Gold, Ounces
Derivative [Line Items]
Outstanding forward and future contracts (in ounces)	1,400
Not Designated as Hedging Instrument [Member] | Futures and Forwards Contracts [Member] | Silver, Ounces
Derivative [Line Items]
Outstanding forward and future contracts (in ounces)	100,000