Note 10 - Employee Equity Incentive Plans - Stock Options by Exercise Price Range (Details) - $ / shares		12 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Exercise Price Range 1 [Member]
Exercise price range, lower limit (in dollars per share)		$ 5.01
Exercise price range, upper limit (in dollars per share)		$ 7.75
Options Outstanding Number of Shares Outstanding (in shares)		819,897
Options Outstanding Weighted Average Contractual Life		2 years 219 days
Options Outstanding Weighted Average Exercise Price per Share (in dollars per share)		$ 6.63
Options Exercisable Number of Shares Exercisable (in shares)		819,897
Options Exercisable Weighted Average Exercise Price per Share (in dollars per share)		$ 6.63
Exercise Price Range 2 [Member]
Exercise price range, lower limit (in dollars per share)		7.76
Exercise price range, upper limit (in dollars per share)		$ 10
Options Outstanding Number of Shares Outstanding (in shares)		1,223,500
Options Outstanding Weighted Average Contractual Life		4 years 292 days
Options Outstanding Weighted Average Exercise Price per Share (in dollars per share)		$ 9.33
Options Exercisable Number of Shares Exercisable (in shares)		1,017,750
Options Exercisable Weighted Average Exercise Price per Share (in dollars per share)		$ 9.29
Exercise Price Range 3 [Member]
Exercise price range, lower limit (in dollars per share)		10.01
Exercise price range, upper limit (in dollars per share)		$ 12.50
Options Outstanding Number of Shares Outstanding (in shares)		2,448,000
Options Outstanding Weighted Average Contractual Life		6 years 219 days
Options Outstanding Weighted Average Exercise Price per Share (in dollars per share)		$ 11.42
Options Exercisable Number of Shares Exercisable (in shares)		1,331,916
Options Exercisable Weighted Average Exercise Price per Share (in dollars per share)		$ 11.52
Exercise Price Range 4 [Member]
Exercise price range, lower limit (in dollars per share)		12.51
Exercise price range, upper limit (in dollars per share)		$ 13.37
Options Outstanding Number of Shares Outstanding (in shares)		743,000
Options Outstanding Weighted Average Contractual Life		6 years 36 days
Options Outstanding Weighted Average Exercise Price per Share (in dollars per share)		$ 12.96
Options Exercisable Number of Shares Exercisable (in shares)		450,000
Options Exercisable Weighted Average Exercise Price per Share (in dollars per share)		$ 12.69
Exercise price range, lower limit (in dollars per share)		5.01
Exercise price range, upper limit (in dollars per share)		$ 13.37
Options Outstanding Number of Shares Outstanding (in shares)	[1]	5,234,397	4,942,511	5,201,635	5,327,473
Options Outstanding Weighted Average Contractual Life		5 years 182 days
Options Outstanding Weighted Average Exercise Price per Share (in dollars per share)		$ 10.40	$ 10.37	$ 10.22	$ 10.04
Options Exercisable Number of Shares Exercisable (in shares)		3,619,563
Options Exercisable Weighted Average Exercise Price per Share (in dollars per share)		$ 9.93

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