Debt (Details) (USD $)	3 Months Ended		6 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Jun. 30, 2011
Debt [Abstract]
Maximum borrowing capacity	$ 160,000,000		$ 160,000,000		$ 160,000,000
Maximum borrowing capacity on obtaining consent of the issuing bank	260,000,000		260,000,000		260,000,000
Line of credit facility, expiration date			October 2012
Line of credit facility, amount outstanding	0		0		0
Standby letters of credit, amount outstanding	6,700,000		6,700,000
Interest paid	$ 0	$ 0	$ 0	$ 0
Maximum leverage ratio			3
Minimum interest coverage ratio			2.5