Derivative Instruments (Details) In Thousands, except Per Share data, unless otherwise specified		12 Months Ended					12 Months Ended				12 Months Ended					12 Months Ended
	Jun. 30, 2012 USD ($)	Jun. 30, 2012 Interest Rate Derivatives [Member] Interest Expense [Member] USD ($)	Jun. 30, 2011 Interest Rate Derivatives [Member] Interest Expense [Member] USD ($)	Jun. 30, 2010 Interest Rate Derivatives [Member] Interest Expense [Member] USD ($)	Jun. 30, 2012 Foreign Exchange Forward [Member] USD ($)	Jun. 30, 2012 Foreign Exchange Forward [Member] EUR (€)	Jun. 30, 2012 Foreign Exchange Forward [Member] Foreign Exchange Gain (Loss) [Member] USD ($)	Jun. 30, 2011 Foreign Exchange Forward [Member] Foreign Exchange Gain (Loss) [Member] USD ($)	Jun. 30, 2010 Foreign Exchange Forward [Member] Foreign Exchange Gain (Loss) [Member] USD ($)	Jun. 30, 2012 Power Hedges [Member] USD ($)	Jun. 30, 2012 Power Hedges [Member] Cost of Goods Sold [Member] USD ($)	Jun. 30, 2011 Power Hedges [Member] Cost of Goods Sold [Member] USD ($)	Jun. 30, 2010 Power Hedges [Member] Cost of Goods Sold [Member] USD ($)	Jun. 30, 2012 Canadian Dollar [Member]	Jun. 30, 2012 Euro [Member]	Jun. 30, 2011 Power Hedge June 2010 [Member] USD ($)	Jun. 30, 2011 Power Hedge October 2010 [Member] USD ($)
Derivative [Line Items]
Revolving credit facility face value	$ 300,000
Average forward exchange rate														1.30	1.00
Expiration date of agreement																Jun. 30, 2012	Jun. 30, 2013
Notional amount of electricity supplied per agreement (in MWh)																175,440	87,600
Electricity supplied as a percentage of plant's total power requirement (in hundredths)																20.00%
Fixed power rate, price per MWh																$ 39.60	$ 39.95
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized		(119)	(252)	(1,231)			20	(190)	772		(1,272)	173	(243)
Notional value						7,500
Fair value of derivatives					$ 20					$ 742