Note 11. Business Segments and Significant Customers (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011
Derivative, Gain on Derivative	$ 38.0
Foward Contracts For Lead And Zinc [Member]
Derivative, Gain on Derivative	$ 7.1

Increase in the fair value of the derivative or group of derivatives included in earnings in the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5618551-113959

Name:	us-gaap_DerivativeGainOnDerivative
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration