Note 3 - Fair Value - Assets and Liabilities Measured at Fair Value (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands		Sep. 30, 2017	Mar. 31, 2017
Money market funds	[1],[2]	$ 96,780	$ 90,752
Marketable equity securities	[2],[3]	1,649	1,771
Auction rate preferred securities	[2],[3]	350	350
Total assets measured at fair value	[2]	98,779	92,873
Fair Value, Inputs, Level 1 [Member]
Money market funds	[1],[2]	96,780	90,752
Marketable equity securities	[2],[3]	1,649	1,771
Auction rate preferred securities	[2],[3]
Total assets measured at fair value	[2]	98,429	92,523
Fair Value, Inputs, Level 2 [Member]
Money market funds	[1],[2]
Marketable equity securities	[2],[3]
Auction rate preferred securities	[2],[3]	350	350
Total assets measured at fair value	[2]	$ 350	$ 350

[1] Included in "Cash and cash equivalents" on our unaudited condensed consolidated balance sheets.

[2] We did not have any recurring fair value measurements of assets or liabilities whose fair value was measured using significant unobservable inputs.

[3] Included in "Other assets" on our unaudited condensed consolidated balance sheets.