Note 11. Business Segments and Significant Customers (Detail) - Percentage Of Sales To Major Customers	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Teck Metals Ltd. [Member]
Major Customer	51.10%	29.60%	43.60%
Korea Zinc [Member]
Major Customer	18.40%	20.70%	23.40%
Trafigura AG [Member]
Major Customer	12.40%	17.40%