Debt Debt (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2013		Dec. 31, 2012
Schedule of Debt Instruments [Line Items]
Industrial revenue bonds	$ 7,815		$ 7,815
Current portion of long-term debt	2,603		0
Revolving credit facility	16,725		0
TOTAL	273,585		273,766
Industrial revenue bonds due 2028 [Member] | Short-term Debt [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount	0	[1]	0	[1]
Debt Instrument, Maturity Date	Apr. 01, 2028	[1]	Apr. 01, 2028	[1]
Debt Instrument, Interest Rate, Effective Percentage Rate Range, Maximum	12.00%	[1]	12.00%	[1]
Industrial revenue bonds	7,815	[1]	7,815	[1]
Debt Instrument, Interest Rate, Stated Percentage	0.27%
Senior secured notes due June 01, 2021 [Member] | Long-term Debt [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount	3,558		0
Debt Instrument, Maturity Date	Jun. 01, 2021
Secured Long-term Debt, Noncurrent	246,442		0
Debt Instrument, Interest Rate, Stated Percentage	7.50%		0.00%
Senior secured notes due May 15, 2014 [Member] | Long-term Debt [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount	0		1,625
Debt Instrument, Maturity Date			May 15, 2014
Secured Long-term Debt, Noncurrent	0		247,979
Debt Instrument, Interest Rate, Stated Percentage	0.00%		8.00%
Senior unsecured notes due August 15, 2014 [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.50%
Senior unsecured notes due August 15, 2014 [Member] | Long-term Debt [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount	0		0
Debt Instrument, Maturity Date			Aug. 15, 2014
Unsecured Long-term Debt, Noncurrent	0		2,603
Debt Instrument, Interest Rate, Stated Percentage	0.00%		7.50%
Senior unsecured notes due August 15, 2014 [Member] | Short-term Debt [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount	0		0
Debt Instrument, Maturity Date	Aug. 15, 2014
Current portion of long-term debt	2,603		0
Debt Instrument, Interest Rate, Stated Percentage	7.50%		0.00%
Contingent obligation [Member]
Schedule of Debt Instruments [Line Items]
E.ON Contingent Obligation	0		(15,369)
Contingent obligation [Member] | Long-term Debt [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Unamortized Discount	0	[2]	0	[2]
Debt Instrument, Maturity Date	Dec. 31, 2028	[2]	Dec. 31, 2028	[2]
E.ON Contingent Obligation	0	[2]	15,369	[2]
Debt Instrument, Interest Rate, Stated Percentage	10.94%	[2]	10.94%	[2]
Revolving Credit Facility [Member] | Long-term Debt [Member]
Schedule of Debt Instruments [Line Items]
Debt Instrument, Term	5 years
Revolving credit facility	$ 16,725	[3]	$ 0	[3]

[1] The IRBs are classified as current liabilities because they are remarketed weekly and could be required to be repaid upon demand if there is a failed remarketing. The IRB interest rate at September 30, 2013 was 0.27%.

[2] E.ON contingent obligation principal and interest payments are payable based on CAKY’s operating level and the LME price for primary aluminum. See E.ON contingent obligation below and Note 4 Fair value measurements for additional information.

[3] Borrowings under the revolving line of credit bear interest, at our option, at LIBOR or a base rate, plus, in each case, an applicable interest margin. The applicable interest margin is determined based on the average daily availability for the immediately preceding quarter.