Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2010
Consolidated Statements of Income [Abstract]
Net sales	$ 705,544		$ 641,863		$ 472,658
Cost of goods sold	552,873		488,018		390,093
Selling, general, and administrative expenses	61,623		54,739		47,875
Research and development	127		87		200
Business interruption insurance recovery	(450)		0		0
Restructuring charges	0		0		(81)
(Gain) loss on sale of business	(54)		4,249		(19,715)
Operating income	91,425		94,770		54,286
Other income (expense):
Interest income	243		214		318
Interest expense, net of capitalized interest	(7,610)	[1]	(3,198)	[1]	(4,372)	[1]
Foreign exchange gain (loss)	1,191		(390)		3,811
Other income	1,387		1,318		764
Income before provision for income taxes	86,636		92,714		54,807
Provision for income taxes	28,760		35,988		20,539
Net income	57,876		56,726		34,268
Income attributable to noncontrolling interest, net of tax	(3,306)		(3,918)		(167)
Net income attributable to Globe Specialty Metals, Inc.	$ 54,570		$ 52,808		$ 34,101
Weighted average shares outstanding:
Basic (in shares)	75,038,674		74,924,947		73,511,696
Diluted (in shares)	76,623,892		76,624,345		74,770,147
Earnings per common share:
Basic (in dollars per share)	$ 0.73		$ 0.70		$ 0.46
Diluted (in dollars per share)	$ 0.71		$ 0.69		$ 0.46
Cash dividends declared per common share (in dollars per share)	$ 0.20		$ 0.15		$ 0

[1] Net of capitalized interest.