Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2023		Jun. 30, 2023
Accounts and other receivables, allowance for credit loss	$ 0		$ 0
Investments in available-for-sale debt securities, amortized cost	7,056	[1]	7,729
Investments in available-for-sale debt securities, allowance for credit loss	$ 0		$ 0
Treasury shares (in shares)	1,753,239		1,370,325
Common Class A [Member]
Common Stock, Par value (in dollars per share)	$ 0.025		$ 0.025
Common Stock, Shares Authorized (in shares)	28,000,000		28,000,000
Common Stock, Shares, Issued (in shares)	13,866,999		13,866,999
Common Stock, Shares, Outstanding (in shares)	12,113,760		12,496,674
Common Class B [Member]
Common Stock, Par value (in dollars per share)	$ 0.025		$ 0.025
Common Stock, Shares Authorized (in shares)	4,500,000		4,500,000
Common Stock, Shares, Issued (in shares)	0		0
Common Class C [Member]
Common Stock, Par value (in dollars per share)	$ 0.025		$ 0.025
Common Stock, Shares Authorized (in shares)	3,500,000		3,500,000
Common Stock, Shares, Issued (in shares)	2,068,549		2,068,549
Common Stock, Shares, Outstanding (in shares)	2,068,549		2,068,549

[1] Principal payments of $750,000 are due quarterly with a final maturity date in January 2026.