Note 5 - Fair Value Measurements - Fair Value Measurements (Details) - USD ($) $ in Thousands		Mar. 31, 2024	Jun. 30, 2023
Total		$ 144,508	$ 134,500
US Treasury Bill Securities [Member]
Investments (2)	[1]	82,356	110,577
US Treasury Notes Securities [Member]
Investments (2)	[1]	34,867
Money Market Funds [Member]
Corporate money market funds (1)	[2]	27,285	23,923
Fair Value, Inputs, Level 1 [Member]
Total		27,285	23,923
Fair Value, Inputs, Level 1 [Member] | US Treasury Bill Securities [Member]
Investments (2)	[1]	0	0
Fair Value, Inputs, Level 1 [Member] | US Treasury Notes Securities [Member]
Investments (2)	[1]	0
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Corporate money market funds (1)	[2]	27,285	23,923
Fair Value, Inputs, Level 2 [Member]
Total		117,223	110,577
Fair Value, Inputs, Level 2 [Member] | US Treasury Bill Securities [Member]
Investments (2)	[1]	82,356	110,577
Fair Value, Inputs, Level 2 [Member] | US Treasury Notes Securities [Member]
Investments (2)	[1]	34,867
Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Corporate money market funds (1)	[2]	0	0
Fair Value, Inputs, Level 3 [Member]
Total		0	0
Fair Value, Inputs, Level 3 [Member] | US Treasury Bill Securities [Member]
Investments (2)	[1]	0	0
Fair Value, Inputs, Level 3 [Member] | US Treasury Notes Securities [Member]
Investments (2)	[1]	0
Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]
Corporate money market funds (1)	[2]	$ 0	$ 0

[1] We have current and non-current debt securities (U.S. Treasury bills and notes) intended to enhance returns on our cash as well as to fund future obligations. All unrealized gains and losses were included in Accumulated other comprehensive loss within our consolidated balance sheets. There were no material gross unrealized gains or losses on the investments at March 31, 2024 or June 30, 2023.

[2] Our corporate money market funds are readily convertible into cash and the net asset value of each fund on the last day of the quarter is used to determine its fair value.