Note 11 - Employee Equity Incentive Plans - Fair Value and Assumptions (Details) - $ / shares		3 Months Ended
		Jun. 30, 2015	Jun. 30, 2014
Employee Stock Option [Member]
Weighted average estimated fair value of grant per share (in dollars per share)	[1]	$ 6.32
Risk-free interest rate	[1]	2.00%
Expected term in years	[1]	6 years 273 days
Volatility	[1]	50.70%
Dividend yield	[1]	1.01%
Employee Stock Purchase Plan 1999 [Member]
Weighted average estimated fair value of grant per share (in dollars per share)		$ 3.15	$ 2.90
Risk-free interest rate		0.10%	0.10%
Expected term in years		1 year	182 days
Volatility		33.70%	34.50%
Dividend yield		1.11%	1.06%

[1] No stock options were granted during the quarters ended June 30, 2014.