Condensed consolidating financial information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012	Dec. 31, 2012
Guarantor Obligations [Line Items]
Percentage of subsidiary guarantor owned by company (in hundredths)				100.00%
Assets:
Cash and cash equivalents	$ 140,801		$ 173,375	$ 140,801		$ 173,375
Restricted cash	3,273			3,273			258
Accounts receivable — net	51,247			51,247			50,667
Due from affiliates	24,955			24,955			37,870
Inventories	231,505	[1]		231,505	[1]		159,925	[1]
Prepaid and other current assets	40,708			40,708			34,975
Deferred taxes - current portion	19,720			19,720			19,726
Total current assets	512,209			512,209			487,397
Investment in subsidiaries	0			0			0
Property, plant and equipment — net	1,239,201			1,239,201			1,188,214
Due from affiliates – less current portion	0			0			0
Other assets	108,221			108,221			100,715
TOTAL	1,859,631			1,859,631			1,776,326
Liabilities and shareholders' equity:
Accounts payable, trade	105,950			105,950			75,370
Due to affiliates	71,739			71,739			39,737
Accrued and other current liabilities	72,921			72,921			40,099
Accrued employee benefits costs	17,060			17,060			18,683
Industrial revenue bonds	7,815			7,815			7,815
Current portion of long-term debt	2,603			2,603			0
Total current liabilities	278,088			278,088			181,704
Senior notes payable	246,442			246,442			250,582
Revolving credit facility	16,725			16,725			0
Accrued pension benefit costs — less current portion	59,724			59,724			67,878
Accrued postretirement benefits costs — less current portion	144,025			144,025			143,105
Other liabilities/intercompany loan	37,184			37,184			40,162
Deferred taxes	111,922			111,922			110,252
Total noncurrent liabilities	616,022			616,022			611,979
Shareholders' equity:
Series A Preferred stock	1			1			1
Common stock	935			935			933
Additional paid-in capital	2,508,456			2,508,456			2,507,454
Treasury stock, at cost	(49,924)			(49,924)			(49,924)
Accumulated other comprehensive loss	(138,680)			(138,680)			(151,192)
Retained earnings (accumulated deficit)	(1,355,267)			(1,355,267)			(1,324,629)
Total shareholders’ equity	965,521			965,521			982,643
Total	1,859,631			1,859,631			1,776,326
Net sales:
Third-party customers	271,016		170,023	680,480		542,884
Related parties	128,912		134,612	372,659		411,560
Sales Revenue – net	399,928		304,635	1,053,139		954,444
Cost of goods sold	387,574		301,385	1,028,901		924,645
Gross profit	12,354		3,250	24,238		29,799
Other operating expenses – net	2,174		7,388	6,288		14,926
Selling, general and administrative expenses	14,422		9,182	45,875		24,792
Operating income (loss)	(4,242)		(13,320)	(27,925)		(9,919)
Interest expense – third party	(5,406)		(6,041)	(17,706)		(17,966)
Interest expense – affiliates	0		0	0		0
Interest income – third party	141		72	458		324
Interest income – affiliates	0		0	0		62
Net gain on forward and derivative contracts	440		(340)	16,151		(4,049)
Gain on bargain purchase	0		0	5,253		0
Loss on early extinguishment of debt	0		0	(3,272)		0
Other income (expense) – net	213		7,648	(1,001)		8,115
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries and joint ventures	(8,854)		(11,981)	(28,042)		(23,433)
Income tax expense	(1,384)		(1,168)	(4,714)		(7,384)
Income (loss) before equity in earnings (loss) of subsidiaries and joint ventures	(10,238)		(13,149)	(32,756)		(30,817)
Equity in earnings (loss) of subsidiaries and joint ventures	731		1,126	2,118		2,116
Net loss	(9,507)		(12,023)	(30,638)		(28,701)
Other comprehensive income before income tax effect	866		1,556	13,660		4,842
Income tax effect	(383)		(382)	(1,148)		(1,147)
Other comprehensive income (loss)	483		1,174	12,512		3,695
Comprehensive income (loss)	(9,024)		(10,849)	(18,126)		(25,006)
CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS
Net cash provided by (used in) operating activities				42,458		21,085
Purchase of property, plant and equipment				(31,994)		(10,399)
Nordural expansion — Helguvik				(2,855)		(5,474)
Purchase of carbon anode assets and improvements				(8,519)		(14,185)
Purchase of Sebree smelter				(48,058)		0
Investments in and advances to joint ventures				0		(275)
Dividends and payments received on advances to joint ventures				0		3,166
Proceeds from sale of property, plant and equipment				515		89
Restricted and other cash deposits				(3,015)		0
Net cash used in investing activities				(93,926)		(27,078)
Financing activities:
Repayment of debt				(249,604)		0
Proceeds from issuance of debt				246,330		0
Borrowings under revolving credit facility				16,725		18,076
Repayments under revolving credit facility				0		(18,076)
Debt issuance costs				(3,994)		0
Debt retirement costs				1,208		0
Intercompany transactions				0		0
Repurchase of common stock				0		(4,033)
Issuance of common stock — net				44		0
Net cash provided by (used in) financing activities				8,293		(4,033)
Change in cash and cash equivalents				(43,175)		(10,026)
Cash and cash equivalents, beginning of the period				183,976		183,401
Cash and cash equivalents, end of the period	140,801		173,375	140,801		173,375
Senior unsecured notes due August 15, 2014 [Member]
Guarantor Obligations [Line Items]
Interest rate (in hundredths)	7.50%			7.50%
Combined Guarantor Subsidiaries [Member]
Assets:
Cash and cash equivalents	0		0	0		0
Restricted cash	790			790			258
Accounts receivable — net	50,157			50,157			38,328
Due from affiliates	610,588			610,588			604,008
Inventories	158,620			158,620			97,847
Prepaid and other current assets	4,199			4,199			4,421
Deferred taxes - current portion	0			0			0
Total current assets	824,354			824,354			744,862
Investment in subsidiaries	50,696			50,696			40,335
Property, plant and equipment — net	354,595			354,595			313,090
Due from affiliates – less current portion	0			0			0
Other assets	17,603			17,603			17,616
TOTAL	1,247,248			1,247,248			1,115,903
Liabilities and shareholders' equity:
Accounts payable, trade	66,212			66,212			37,301
Due to affiliates	2,161,803			2,161,803			2,098,320
Accrued and other current liabilities	39,678			39,678			13,031
Accrued employee benefits costs	13,495			13,495			15,926
Industrial revenue bonds	7,815			7,815			7,815
Current portion of long-term debt	0			0
Total current liabilities	2,289,003			2,289,003			2,172,393
Senior notes payable	0			0			0
Revolving credit facility	0			0
Accrued pension benefit costs — less current portion	29,188			29,188			36,087
Accrued postretirement benefits costs — less current portion	137,388			137,388			137,184
Other liabilities/intercompany loan	57,871			57,871			65,377
Deferred taxes	0			0			0
Total noncurrent liabilities	224,447			224,447			238,648
Shareholders' equity:
Series A Preferred stock	0			0			0
Common stock	60			60			60
Additional paid-in capital	370,467			370,467			303,659
Treasury stock, at cost	0			0			0
Accumulated other comprehensive loss	(133,371)			(133,371)			(146,862)
Retained earnings (accumulated deficit)	(1,503,358)			(1,503,358)			(1,451,995)
Total shareholders’ equity	(1,266,202)			(1,266,202)			(1,295,138)
Total	1,247,248			1,247,248			1,115,903
Net sales:
Third-party customers	224,571		123,525	535,655		391,100
Related parties	71,399		75,590	189,679		226,589
Sales Revenue – net	295,970		199,115	725,334		617,689
Cost of goods sold	303,521		210,417	765,101		640,650
Gross profit	(7,551)		(11,302)	(39,767)		(22,961)
Other operating expenses – net	2,174		7,388	6,288		14,926
Selling, general and administrative expenses	10,585		7,530	35,229		23,747
Operating income (loss)	(20,310)		(26,220)	(81,284)		(61,634)
Interest expense – third party	(5,406)		(6,041)	(17,706)		(17,966)
Interest expense – affiliates	13,950		15,860	42,967		48,108
Interest income – third party	4		4	35		19
Interest income – affiliates						0
Net gain on forward and derivative contracts	440		(340)	16,151		(4,049)
Gain on bargain purchase				5,253
Loss on early extinguishment of debt				(3,272)
Other income (expense) – net	(25)		(48)	(34)		750
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries and joint ventures	(11,347)		(16,785)	(37,890)		(34,772)
Income tax expense	685		964	(5,099)		279
Income (loss) before equity in earnings (loss) of subsidiaries and joint ventures	(10,662)		(15,821)	(42,989)		(34,493)
Equity in earnings (loss) of subsidiaries and joint ventures	(3,108)		(638)	(8,374)		(482)
Net loss	(13,770)		(16,459)	(51,363)		(34,975)
Other comprehensive income before income tax effect	2,093		1,339	13,183		4,141
Income tax effect	(375)		(4)	(1,123)		(605)
Other comprehensive income (loss)	1,718		1,335	12,060		3,536
Comprehensive income (loss)	(12,052)		(15,124)	(39,303)		(31,439)
CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS
Net cash provided by (used in) operating activities				54,782		11,824
Purchase of property, plant and equipment				(10,400)		(4,102)
Nordural expansion — Helguvik				0		0
Purchase of carbon anode assets and improvements				0		(14,185)
Purchase of Sebree smelter				0
Investments in and advances to joint ventures						0
Dividends and payments received on advances to joint ventures						0
Proceeds from sale of property, plant and equipment				10		0
Restricted and other cash deposits				(532)
Net cash used in investing activities				(10,922)		(18,287)
Financing activities:
Repayment of debt				0
Proceeds from issuance of debt				0
Borrowings under revolving credit facility				0		0
Repayments under revolving credit facility						0
Debt issuance costs				0
Debt retirement costs				0
Intercompany transactions				(43,860)		6,463
Repurchase of common stock						0
Issuance of common stock — net				0
Net cash provided by (used in) financing activities				(43,860)		6,463
Change in cash and cash equivalents				0		0
Cash and cash equivalents, beginning of the period				0		0
Cash and cash equivalents, end of the period	0		0	0		0
Combined Non-Guarantor Subsidiaries [Member]
Assets:
Cash and cash equivalents	64,366		137,992	64,366		137,992
Restricted cash	2,483			2,483			0
Accounts receivable — net	1,090			1,090			12,339
Due from affiliates	39,991			39,991			38,328
Inventories	72,885			72,885			62,078
Prepaid and other current assets	31,456			31,456			30,650
Deferred taxes - current portion	19,726			19,726			17,799
Total current assets	231,997			231,997			271,210
Investment in subsidiaries	0			0			0
Property, plant and equipment — net	883,232			883,232			874,559
Due from affiliates – less current portion	30,479			30,479			3,588
Other assets	53,596			53,596			45,474
TOTAL	1,199,304			1,199,304			1,194,831
Liabilities and shareholders' equity:
Accounts payable, trade	38,383			38,383			37,627
Due to affiliates	135,587			135,587			105,945
Accrued and other current liabilities	13,678			13,678			31,332
Accrued employee benefits costs	0			0			0
Industrial revenue bonds	0			0			0
Current portion of long-term debt	0			0
Total current liabilities	187,648			187,648			174,904
Senior notes payable	0			0			0
Revolving credit facility	0			0
Accrued pension benefit costs — less current portion	0			0			0
Accrued postretirement benefits costs — less current portion	0			0			0
Other liabilities/intercompany loan	572,417			572,417			614,585
Deferred taxes	111,922			111,922			109,011
Total noncurrent liabilities	684,339			684,339			723,596
Shareholders' equity:
Series A Preferred stock	0			0			0
Common stock	12			12			12
Additional paid-in capital	169,493			169,493			150,743
Treasury stock, at cost	0			0			0
Accumulated other comprehensive loss	(1,640)			(1,640)			(1,525)
Retained earnings (accumulated deficit)	159,452			159,452			147,101
Total shareholders’ equity	327,317			327,317			296,331
Total	1,199,304			1,199,304			1,194,831
Net sales:
Third-party customers	46,445		46,498	144,825		151,784
Related parties	57,513		59,022	182,980		184,971
Sales Revenue – net	103,958		105,520	327,805		336,755
Cost of goods sold	84,053		90,968	263,800		283,995
Gross profit	19,905		14,552	64,005		52,760
Other operating expenses – net	0		0	0		0
Selling, general and administrative expenses	3,837		1,652	10,646		1,045
Operating income (loss)	16,068		12,900	53,359		51,715
Interest expense – third party	0		0	0		0
Interest expense – affiliates	(13,950)		(15,860)	(42,967)		(48,108)
Interest income – third party	137		68	423		305
Interest income – affiliates						62
Net gain on forward and derivative contracts	0		0	0		0
Gain on bargain purchase				0
Loss on early extinguishment of debt				0
Other income (expense) – net	238		7,696	(967)		7,365
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries and joint ventures	2,493		4,804	9,848		11,339
Income tax expense	(2,069)		(2,132)	385		(7,663)
Income (loss) before equity in earnings (loss) of subsidiaries and joint ventures	424		2,672	10,233		3,676
Equity in earnings (loss) of subsidiaries and joint ventures	731		1,126	2,118		2,116
Net loss	1,155		3,798	12,351		5,792
Other comprehensive income before income tax effect	(46)		(47)	(139)		(140)
Income tax effect	8		9	25		26
Other comprehensive income (loss)	(38)		(38)	(114)		(114)
Comprehensive income (loss)	1,117		3,760	12,237		5,678
CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS
Net cash provided by (used in) operating activities				(12,324)		9,261
Purchase of property, plant and equipment				(20,408)		(6,219)
Nordural expansion — Helguvik				(2,855)		(5,474)
Purchase of carbon anode assets and improvements				(8,519)		0
Purchase of Sebree smelter				0
Investments in and advances to joint ventures						0
Dividends and payments received on advances to joint ventures						0
Proceeds from sale of property, plant and equipment				505		89
Restricted and other cash deposits				(2,483)
Net cash used in investing activities				(33,760)		(11,604)
Financing activities:
Repayment of debt				0
Proceeds from issuance of debt				0
Borrowings under revolving credit facility				0		0
Repayments under revolving credit facility						0
Debt issuance costs				0
Debt retirement costs				0
Intercompany transactions				434		(18,822)
Repurchase of common stock						0
Issuance of common stock — net				0
Net cash provided by (used in) financing activities				434		(18,822)
Change in cash and cash equivalents				(45,650)		(21,165)
Cash and cash equivalents, beginning of the period				110,016		159,157
Cash and cash equivalents, end of the period	64,366		137,992	64,366		137,992
Century Aluminum Company [Member]
Assets:
Cash and cash equivalents	76,435		35,383	76,435		35,383
Restricted cash	0			0			0
Accounts receivable — net	0			0			0
Due from affiliates	2,339,683			2,339,683			2,391,249
Inventories	0			0			0
Prepaid and other current assets	5,053			5,053			8,063
Deferred taxes - current portion	0			0			0
Total current assets	2,421,171			2,421,171			2,473,272
Investment in subsidiaries	(959,581)			(959,581)			(1,039,141)
Property, plant and equipment — net	1,793			1,793			916
Due from affiliates – less current portion	0			0			0
Other assets	32,274			32,274			37,027
TOTAL	1,495,657			1,495,657			1,472,074
Liabilities and shareholders' equity:
Accounts payable, trade	1,355			1,355			442
Due to affiliates	202,075			202,075			193,788
Accrued and other current liabilities	17,638			17,638			1,967
Accrued employee benefits costs	3,565			3,565			2,757
Industrial revenue bonds	0			0			0
Current portion of long-term debt	2,603			2,603
Total current liabilities	227,236			227,236			198,954
Senior notes payable	246,442			246,442			250,582
Revolving credit facility	16,725			16,725
Accrued pension benefit costs — less current portion	30,536			30,536			31,791
Accrued postretirement benefits costs — less current portion	6,637			6,637			5,921
Other liabilities/intercompany loan	2,560			2,560			2,183
Deferred taxes	0			0			0
Total noncurrent liabilities	302,900			302,900			290,477
Shareholders' equity:
Series A Preferred stock	1			1			1
Common stock	935			935			933
Additional paid-in capital	2,508,456			2,508,456			2,507,454
Treasury stock, at cost	(49,924)			(49,924)			(49,924)
Accumulated other comprehensive loss	(138,680)			(138,680)			(151,192)
Retained earnings (accumulated deficit)	(1,355,267)			(1,355,267)			(1,324,629)
Total shareholders’ equity	965,521			965,521			982,643
Total	1,495,657			1,495,657			1,472,074
Net sales:
Third-party customers	0		0	0		0
Related parties	0		0	0		0
Sales Revenue – net	0		0	0		0
Cost of goods sold	0		0	0		0
Gross profit	0		0	0		0
Other operating expenses – net	0		0	0		0
Selling, general and administrative expenses	0		0	0		0
Operating income (loss)	0		0	0		0
Interest expense – third party	0		0	0		0
Interest expense – affiliates	0		0	0		0
Interest income – third party	0		0	0		0
Interest income – affiliates						0
Net gain on forward and derivative contracts	0		0	0		0
Gain on bargain purchase				0
Loss on early extinguishment of debt				0
Other income (expense) – net	0		0	0		0
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries and joint ventures	0		0	0		0
Income tax expense	0		0	0		0
Income (loss) before equity in earnings (loss) of subsidiaries and joint ventures	0		0	0		0
Equity in earnings (loss) of subsidiaries and joint ventures	(9,507)		(12,023)	(30,638)		(28,701)
Net loss	(9,507)		(12,023)	(30,638)		(28,701)
Other comprehensive income before income tax effect	866		1,556	13,660		4,842
Income tax effect	(383)		(382)	(1,148)		(1,147)
Other comprehensive income (loss)	483		1,174	12,512		3,695
Comprehensive income (loss)	(9,024)		(10,849)	(18,126)		(25,006)
CONDENSED CONSOLIDATING STATEMENT OF CASH FLOWS
Net cash provided by (used in) operating activities				0		0
Purchase of property, plant and equipment				(1,186)		(78)
Nordural expansion — Helguvik				0		0
Purchase of carbon anode assets and improvements				0		0
Purchase of Sebree smelter				(48,058)
Investments in and advances to joint ventures						(275)
Dividends and payments received on advances to joint ventures						3,166
Proceeds from sale of property, plant and equipment				0		0
Restricted and other cash deposits				0
Net cash used in investing activities				(49,244)		2,813
Financing activities:
Repayment of debt				(249,604)
Proceeds from issuance of debt				246,330
Borrowings under revolving credit facility				16,725		18,076
Repayments under revolving credit facility						(18,076)
Debt issuance costs				(3,994)
Debt retirement costs				1,208
Intercompany transactions				43,426		12,359
Repurchase of common stock						(4,033)
Issuance of common stock — net				44
Net cash provided by (used in) financing activities				51,719		8,326
Change in cash and cash equivalents				2,475		11,139
Cash and cash equivalents, beginning of the period				73,960		24,244
Cash and cash equivalents, end of the period	76,435		35,383	76,435		35,383
Reclassifications and Eliminations [Member]
Assets:
Cash and cash equivalents	0			0
Restricted cash	0			0			0
Accounts receivable — net	0			0			0
Due from affiliates	(2,965,307)			(2,965,307)			(2,995,715)
Inventories	0			0			0
Prepaid and other current assets	0			0			(8,159)
Deferred taxes - current portion	(6)			(6)			1,927
Total current assets	(2,965,313)			(2,965,313)			(3,001,947)
Investment in subsidiaries	908,885			908,885			998,806
Property, plant and equipment — net	(419)			(419)			(351)
Due from affiliates – less current portion	(30,479)			(30,479)			(3,588)
Other assets	4,748			4,748			598
TOTAL	(2,082,578)			(2,082,578)			(2,006,482)
Liabilities and shareholders' equity:
Accounts payable, trade	0			0			0
Due to affiliates	(2,427,726)			(2,427,726)			(2,358,316)
Accrued and other current liabilities	1,927			1,927			(6,231)
Accrued employee benefits costs	0			0			0
Industrial revenue bonds	0			0			0
Current portion of long-term debt	0			0
Total current liabilities	(2,425,799)			(2,425,799)			(2,364,547)
Senior notes payable	0			0			0
Revolving credit facility	0			0
Accrued pension benefit costs — less current portion	0			0			0
Accrued postretirement benefits costs — less current portion	0			0			0
Other liabilities/intercompany loan	(595,664)			(595,664)			(641,983)
Deferred taxes	0			0			1,241
Total noncurrent liabilities	(595,664)			(595,664)			(640,742)
Shareholders' equity:
Series A Preferred stock	0			0			0
Common stock	(72)			(72)			(72)
Additional paid-in capital	(539,960)			(539,960)			(454,402)
Treasury stock, at cost	0			0			0
Accumulated other comprehensive loss	135,011			135,011			148,387
Retained earnings (accumulated deficit)	1,343,906			1,343,906			1,304,894
Total shareholders’ equity	938,885			938,885			998,807
Total	(2,082,578)			(2,082,578)			(2,006,482)
Net sales:
Third-party customers	0		0	0		0
Related parties	0		0	0		0
Sales Revenue – net	0		0	0		0
Cost of goods sold	0		0	0		0
Gross profit	0		0	0		0
Other operating expenses – net	0		0	0		0
Selling, general and administrative expenses	0		0	0		0
Operating income (loss)	0		0	0		0
Interest expense – third party	0		0	0		0
Interest expense – affiliates	0		0	0		0
Interest income – third party	0		0	0		0
Interest income – affiliates						0
Net gain on forward and derivative contracts	0		0	0		0
Gain on bargain purchase				0
Loss on early extinguishment of debt				0
Other income (expense) – net	0		0	0		0
Income (loss) before income taxes and equity in earnings (loss) of subsidiaries and joint ventures	0		0	0		0
Income tax expense	0		0	0		0
Income (loss) before equity in earnings (loss) of subsidiaries and joint ventures	0		0	0		0
Equity in earnings (loss) of subsidiaries and joint ventures	12,615		12,661	39,012		29,183
Net loss	12,615		12,661	39,012		29,183
Other comprehensive income before income tax effect	(2,047)		(1,292)	(13,044)		(4,001)
Income tax effect	367		(5)	1,098		579
Other comprehensive income (loss)	(1,680)		(1,297)	(11,946)		(3,422)
Comprehensive income (loss)	10,935		11,364	27,066		25,761
Financing activities:
Cash and cash equivalents, beginning of the period				0
Cash and cash equivalents, end of the period	$ 0			$ 0

[1] The balance at September 30, 2013 includes inventory maintained at the recently acquired Sebree smelter. See Note 2 Acquisition of Sebree aluminum smelter for additional information about the Sebree acquisition.