Summary of Significant Accounting Policies, Textuals (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010	Sep. 30, 2011		Sep. 30, 2010	Dec. 31, 2010
Noncontrolling Interest [Line Items]
Net sales	$ 322.3	[1]	$ 263.4	$ 983.7	[1]	$ 813.3
Summary Of Significant Accounting Policies Additional (Textuals) [Abstract]
Non-cash LIFO benefits (charges)	7.1		2.0	(12.8)		(6.2)
Excess of current cost over the stated LIFO value of inventory	49.2			49.2			36.4
Interest Expense capitalized	0.4		0.8	0.8		2.7
Margin deposits with or from Counterparties	0			0			0
More-likely-than-not threshold	50.00%			50.00%
Percentage of total contributions to multi-employer pension plan	5.00%			5.00%
Anglesey Aluminum Limited [Member]
Noncontrolling Interest [Line Items]
Non-controlling ownership interest in Anglesey Aluminum Limited	49.00%			49.00%
Income (Loss) from Equity Method Investments	0		0	0		0
Carrying amount of Company's investment in Anglesey	0			0			0
Expected period of not resuming the use of equity method of accounting	12 months			12 months
Anglesey Aluminum Limited [Member] | Secondary Aluminum [Member]
Noncontrolling Interest [Line Items]
Net sales	$ 0		$ 0	$ 0		$ 0

[1] The combined results for the quarter and nine months ended September 30, 2011 are as presented in the Statement of Consolidated Income for such periods, reflecting the January 1, 2011 effective date of the Alexco acquisition (see Note 1).