Note 12 - Employee Equity Incentive Plans - Fair Value and Assumptions (Details) - $ / shares		3 Months Ended				9 Months Ended
		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2016		Dec. 31, 2015
Employee Stock Option [Member]
Weighted average estimated fair value of grant per share (in dollars per share)		$ 4.45			[1]	$ 4.42		$ 4.83
Risk-free interest rate		1.70%			[1]	1.50%		1.80%
Expected term in years		6 years 149 days			[1]	6 years 149 days		6 years 164 days
Volatility		39.80%			[1]	40.70%		44.90%
Dividend yield			[2]		[1]	0.40%	[2]	1.20%
Employee Stock Purchase Plan 1999 [Member]
Weighted average estimated fair value of grant per share (in dollars per share)	[3]	$ 2.63		$ 3.54		$ 3.28		$ 3.33
Risk-free interest rate	[3]	0.50%		0.10%		0.40%		0.10%
Expected term in years	[3]	182 days		182 days		182 days		182 days
Volatility	[3]	32.30%		48.20%		37.50%		39.80%
Dividend yield	[3]	0.00%	[2]	1.20%		0.70%	[2]	1.10%

[1] No stock options were granted during the quarter ended December 31, 2015.

[2] No dividends were declared for the quarters ended September 30, 2016 and December 31, 2016.

[3] Under the stock purchase plan, rights to purchase shares are only granted during the first and third quarters of each fiscal year.