Related Party Transactions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Related party transactions
Accounts receivable	$ 5.4		$ 5.4		$ 6.4
Endako Mine Joint Ventrue
Related party transactions
Sales to related party	20.0	27.9	35.3	45.2
Percentage of sales to related party out of total revenue (as a percent)	17.00%	24.60%	15.60%	19.90%
Managment fee income	0	0.1	0.1	0.2
Selling and marketing expenses	0.1	0.2	0.3	0.3
Accounts receivable	$ 5.4		$ 5.4		$ 6.4

The aggregate amount of receivables to be collected from related parties where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth, at the financial statement date. which are usually due within one year (or one business cycle).

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Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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