Investments and Derivative Instruments - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) (Fair Value, Measurements, Recurring, USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Jun. 30, 2012
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Futures, options and other derivative assets	$ 63	[1]	$ 1,626	[1]
Derivative liabilities	2,710	[2]	410	[2]
Derivative liabilities - interest rate swap	40
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Futures, options and other derivative assets	0	[1]	0	[1]
Derivative liabilities	0	[2]	0	[2]
Derivative liabilities - interest rate swap	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Futures, options and other derivative assets	63	[1]	1,626	[1]
Derivative liabilities	2,710	[2]	410	[2]
Derivative liabilities - interest rate swap	40
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Futures, options and other derivative assets	0	[1]	0	[1]
Derivative liabilities	0	[2]	0	[2]
Derivative liabilities - interest rate swap	0
Preferred Stock | Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stock	20,507	[1]	19,395	[1]
Preferred Stock | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stock	15,408	[1]	14,078	[1]
Preferred Stock | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stock	5,099	[1]	5,317	[1]
Preferred Stock | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stock	$ 0	[1]	$ 0	[1]

[1] Included in "Short-term investments" on the consolidated balance sheets.

[2] Included in "Accounts payable" on the consolidated balance sheets.