Note 10 - Employee Equity Incentive Plans - Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014		Aug. 30, 2013	Mar. 31, 2013
Shares available for grant, beginning balance (in shares)		1,747,000	1,930,250	451,713
Options oustanding, beginning balance (in shares)	[1]	4,942,511	5,201,635	5,327,473
Options outstanding, Intrinsic value	[2]	$ 6,456	$ 10,831	$ 8,658			$ 4,273
Weighted average exercise price per share, beginning balance (in dollars per share)		$ 10.37	$ 10.22	$ 10.04
New shares authorized (in shares)				2,000,000	[3]	2,000,000
Plan authorization expired (in shares)				(47,963)
Shares available for grant, options granted (in shares)	[1]	(1,124,000)	(249,000)	(515,000)
Options oustanding, Options granted (in shares)	[1]	1,124,000	249,000	515,000
Weighted average exercise price per share, Options granted (in dollars per share)		$ 11.72	$ 11.83	$ 10.63
Options oustanding, Options exercised (in shares)	[1]	(382,826)	(339,374)	(572,338)
Options exercised, Intrinsic Value	[2]	$ 1,551	$ 1,310	$ 1,695
Weighted average exercise price per share, Options exercised (in dollars per share)		$ 9.02	$ 8.62	$ 8.72
Shares available for grant, Options cancelled (in shares)		14,500	39,750	24,000
Options oustanding, Options cancelled (in shares)	[1]	(14,500)	(94,250)	(34,000)
Weighted average exercise price per share, Options cancelled (in dollars per share)		$ 11.31	$ 11.46	$ 11.42
Shares available for grant, Options expired (in shares)			26,000	17,500
Options oustanding, Options expired (in shares)	[1]	(434,788)	(74,500)	(34,500)
Weighted average exercise price per share, Options expired (in dollars per share)		$ 14.68	$ 11.17	$ 12.62
Shares available for grant, ending balance (in shares)		637,500	1,747,000	1,930,250
Options oustanding, ending balance (in shares)	[1]	5,234,397	4,942,511	5,201,635
Weighted average exercise price per share, ending balance (in dollars per share)		$ 10.40	$ 10.37	$ 10.22

[1] The number of stock options exercised includes shares that were withheld on behalf of employees to satisfy the statutory tax withholding requirements.

[2] Except for options exercised, these amounts represent the difference between the exercise price and $11.22 per share, the closing price of our stock on March 31, 2016 as reported on the NASDAQ Global Select Market, for all in-the-money, outstanding and exercisable options.

[3] On August 30, 2013, our stockholders approved the 2013 Plan, under which 2,000,000 shares of our common stock are reserved for the grant of stock options.