Summary of Significant Accounting Policies - Corrections to Consolidated Statements of Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Net income	$ 2,515	$ 1,806
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	6,256	7,424
Provision for doubtful accounts	7	73
Deferred income taxes	29	37
Net gains from sales of assets	61	(123)
ESOP and share-based compensation expense	1,258	904
Net (gains) losses on derivative instruments and investments	(4,569)	3,768
Change in operating assets and liabilities:
Restricted cash	0	1,824
Purchases of trading securities held for investment	(936)	(1,739)
Proceeds from sales of trading securities held for investment	1,315	1,204
Short-term investments		0
Accounts and notes receivable	(3,949)	1,009
Inventories	(897)	(7,816)
Income tax receivable	30	183
Prepaid expenses and other assets	712	578
Accounts payable	(3,899)	1,907
Accrued payroll expenses and other current liabilities	(6,463)	(3,312)
Accrued postretirement benefits	(230)	190
Other long-term liabilities	(452)	(644)
Net cash (used in) provided by operating activities	(3,823)	7,273
Previously Reported
Net income		1,806
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization		7,424
Provision for doubtful accounts		73
Deferred income taxes		37
Net gains from sales of assets		(123)
ESOP and share-based compensation expense		904
Net (gains) losses on derivative instruments and investments		1,549
Change in operating assets and liabilities:
Restricted cash		1,824
Purchases of trading securities held for investment		0
Proceeds from sales of trading securities held for investment		0
Short-term investments		(1,429)
Accounts and notes receivable		1,009
Inventories		(7,816)
Income tax receivable		183
Prepaid expenses and other assets		578
Accounts payable		1,907
Accrued payroll expenses and other current liabilities		(199)
Accrued postretirement benefits		190
Other long-term liabilities		(644)
Net cash (used in) provided by operating activities		7,273
Adjustments
Net income		0
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization		0
Provision for doubtful accounts		0
Deferred income taxes		0
Net gains from sales of assets		0
ESOP and share-based compensation expense		0
Net (gains) losses on derivative instruments and investments		2,219
Change in operating assets and liabilities:
Restricted cash	0
Purchases of trading securities held for investment		(1,739)
Proceeds from sales of trading securities held for investment		1,204
Short-term investments		1,429
Accounts and notes receivable	0
Inventories	0
Income tax receivable	0
Prepaid expenses and other assets	0
Accounts payable	0
Accrued payroll expenses and other current liabilities		(3,113)
Accrued postretirement benefits		0
Other long-term liabilities		0
Net cash (used in) provided by operating activities		$ 0