Operating Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended												12 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2009	Sep. 30, 2009	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2010
Operating Segments [Abstract]
Number of reportable segments													6
Revenue from External Customer by Product Line [Abstract]
Net sales													$ 705,544		$ 641,863		$ 472,658
Segment Reporting Information [Line Items]
Net Sales													705,544		641,863		472,658
Depreciation and Amortization													34,000		25,055		20,672
Operating Income (Loss)	16,780	19,950	22,230	32,465	29,560	36,753	20,229	8,228	8,187	3,307	30,466	12,326	91,425		94,770		54,286
Interest Income													243		214		318
Interest Expense													(7,610)	[1]	(3,198)	[1]	(4,372)	[1]
Income (Loss) Before Income Taxes													86,636		92,714		54,807
Total Assets	936,747				678,269				607,145				936,747		678,269		607,145
Capital Expenditures													(50,439)		35,039		22,901
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													705,544		641,863		472,658
Long-lived assets	489,978				283,957				271,769				489,978		283,957		271,769
Revenue, Major Customer [Line Items]
Percentage of consolidated net sales (in hundredths)													100.00%		100.00%		100.00%
Dow Corning [Member]
Revenue, Major Customer [Line Items]
Percentage of consolidated net sales (in hundredths)													13.00%		17.00%		30.00%
Noncontrolling interest's ownership interest in consolidated affiliate (in hundredths)	49.00%												49.00%
Term of contractual agreement (in years)	4Y												4Y
Silicon metal to be purchased per calendar year by major customer under original contractual agreement (in metric tons)													30,000
Additional silicon metal to be purchased in calendar year 2009 under amendment to contractual agreement (in metric tons)													17,000
Silicon metal to be purchased in calendar year 2010 under amendment to contractual agreement (in metric tons)													20,000
Settlement cost related to remaining sales obligations													4,276
All other customers [Member]
Revenue, Major Customer [Line Items]
Percentage of consolidated net sales (in hundredths)													87.00%		83.00%		70.00%
United States [Member]
Revenue from External Customer by Product Line [Abstract]
Net sales													625,681		574,181		407,455
Segment Reporting Information [Line Items]
Net Sales													625,681		574,181		407,455
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													625,681		574,181		407,455
Long-lived assets	330,724				224,556				211,876				330,724		224,556		211,876
Argentina [Member]
Revenue from External Customer by Product Line [Abstract]
Net sales													57,154		54,695		42,101
Segment Reporting Information [Line Items]
Net Sales													57,154		54,695		42,101
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													57,154		54,695		42,101
Long-lived assets	31,185				31,054				31,665				31,185		31,054		31,665
Canada [Member]
Revenue from External Customer by Product Line [Abstract]
Net sales													5,520		0		0
Segment Reporting Information [Line Items]
Net Sales													5,520		0		0
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													5,520		0		0
Long-lived assets	100,842				0				0				100,842		0		0
Brazil [Member]
Revenue from External Customer by Product Line [Abstract]
Net sales													0		0		12,820
Segment Reporting Information [Line Items]
Net Sales													0		0		12,820
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													0		0		12,820
China [Member]
Revenue from External Customer by Product Line [Abstract]
Net sales													3,131		899		592
Segment Reporting Information [Line Items]
Net Sales													3,131		899		592
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													3,131		899		592
Long-lived assets	26,288				27,524				27,428				26,288		27,524		27,428
Poland [Member]
Revenue from External Customer by Product Line [Abstract]
Net sales													14,058		12,088		9,690
Segment Reporting Information [Line Items]
Net Sales													14,058		12,088		9,690
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													14,058		12,088		9,690
Long-lived assets	939				823				800				939		823		800
GMI [Member]
Revenue from External Customer by Product Line [Abstract]
Net sales													631,495		549,418		358,279
Segment Reporting Information [Line Items]
Net Sales													631,495		549,418		358,279
Depreciation and Amortization													29,261		20,430		15,812
Operating Income (Loss)													103,542		103,685		41,126
Interest Income													1		5		42
Interest Expense													(5,807)	[1]	1,775	[1]	2,368	[1]
Income (Loss) Before Income Taxes													98,297		102,240		39,107
Total Assets	679,516				384,495				324,680				679,516		384,495		324,680
Capital Expenditures													(36,126)		31,061		18,971
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													631,495		549,418		358,279
Globe Metais [Member]
Revenue from External Customer by Product Line [Abstract]
Net sales													0		15,421		62,126
Segment Reporting Information [Line Items]
Net Sales													0		15,421		62,126
Depreciation and Amortization													0		0		776
Operating Income (Loss)													(2)		397		5,263
Interest Income													0		0		178
Interest Expense													0	[1]	0	[1]	525	[1]
Income (Loss) Before Income Taxes													(2)		398		8,579
Total Assets	0				294				8,192				0		294		8,192
Capital Expenditures													0		0		208
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													0		15,421		62,126
Globe Metales [Member]
Revenue from External Customer by Product Line [Abstract]
Net sales													64,063		62,321		48,959
Segment Reporting Information [Line Items]
Net Sales													64,063		62,321		48,959
Depreciation and Amortization													1,766		1,634		1,820
Operating Income (Loss)													11,332		13,197		10,073
Interest Income													49		0		0
Interest Expense													(1,145)	[1]	1,050	[1]	1,090	[1]
Income (Loss) Before Income Taxes													10,422		12,669		10,069
Total Assets	86,302				82,751				71,790				86,302		82,751		71,790
Capital Expenditures													(1,926)		1,023		996
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													64,063		62,321		48,959
Solsil [Member]
Revenue from External Customer by Product Line [Abstract]
Net sales													0		9,420		20
Segment Reporting Information [Line Items]
Net Sales													0		9,420		20
Depreciation and Amortization													488		488		508
Operating Income (Loss)													(984)		8,670		(1,375)
Interest Income													0		0		0
Interest Expense													0	[1]	0	[1]	30	[1]
Income (Loss) Before Income Taxes													(984)		8,670		(1,405)
Total Assets	30,057				29,191				30,526				30,057		29,191		30,526
Capital Expenditures													(691)		165		(1,410)
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													0		9,420		20
Corporate [Member]
Revenue from External Customer by Product Line [Abstract]
Net sales													0		0		0
Segment Reporting Information [Line Items]
Net Sales													0		0		0
Depreciation and Amortization													424		426		122
Operating Income (Loss)													(27,268)		(29,606)		2,815
Interest Income													777		816		619
Interest Expense													(739)	[1]	470	[1]	317	[1]
Income (Loss) Before Income Taxes													(25,570)		(30,086)		2,836
Total Assets	469,137				403,177				415,184				469,137		403,177		415,184
Capital Expenditures													(2,675)		1,226		1,273
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													0		0		0
Other [Member]
Revenue from External Customer by Product Line [Abstract]
Net sales													28,216		32,325		12,557
Segment Reporting Information [Line Items]
Net Sales													28,216		32,325		12,557
Depreciation and Amortization													2,061		2,077		1,634
Operating Income (Loss)													490		31		(4,273)
Interest Income													0		1		6
Interest Expense													(503)	[1]	511	[1]	569	[1]
Income (Loss) Before Income Taxes													158		428		(5,036)
Total Assets	41,538				43,317				41,508				41,538		43,317		41,508
Capital Expenditures													(418)		1,564		2,863
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													28,216		32,325		12,557
Eliminations [Member]
Revenue from External Customer by Product Line [Abstract]
Net sales													(18,230)		(27,042)		(9,283)
Segment Reporting Information [Line Items]
Net Sales													(18,230)		(27,042)		(9,283)
Depreciation and Amortization													0		0		0
Operating Income (Loss)													4,315		(1,604)		657
Interest Income													(584)		(608)		(527)
Interest Expense													584	[1]	(608)	[1]	(527)	[1]
Income (Loss) Before Income Taxes													4,315		(1,605)		657
Total Assets	(369,803)				(264,956)				(284,735)				(369,803)		(264,956)		(284,735)
Capital Expenditures													0		0		0
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													(18,230)		(27,042)		(9,283)
Silicon metal [Member]
Revenue from External Customer by Product Line [Abstract]
Net sales													360,726		347,599		296,763
Segment Reporting Information [Line Items]
Net Sales													360,726		347,599		296,763
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													360,726		347,599		296,763
Silicon-based alloys [Member]
Revenue from External Customer by Product Line [Abstract]
Net sales													269,919		236,607		148,092
Segment Reporting Information [Line Items]
Net Sales													269,919		236,607		148,092
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													269,919		236,607		148,092
Other products [Member]
Revenue from External Customer by Product Line [Abstract]
Net sales													74,899		57,657		27,803
Segment Reporting Information [Line Items]
Net Sales													74,899		57,657		27,803
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales													$ 74,899		$ 57,657		$ 27,803

[1] Net of capitalized interest.