Note 8 - Equity - Options Outstanding and Exercisable, By Exercise Range (Details) shares in Thousands	9 Months Ended
	Dec. 31, 2016 $ / shares shares
Lower Range of Exercise Price (in dollars per share)	$ 1.35
Upper Range of Exercise Price (in dollars per share)	$ 18.90
Options Outstanding, Number of Shares (in shares) | shares	4,472
Options Outstanding, Weighted-Average Remaining Contractual Life (Year)	8 years 288 days
Options Vested, Number of Shares (in shares) | shares	912
Options Vested, Weighted-Average Exercise Price per Share (in dollars per share)	$ 5.33
Range 1 [Member]
Lower Range of Exercise Price (in dollars per share)	1.35
Upper Range of Exercise Price (in dollars per share)	$ 1.35
Options Outstanding, Number of Shares (in shares) | shares	106
Options Outstanding, Weighted-Average Remaining Contractual Life (Year)	9 years 164 days
Options Vested, Number of Shares (in shares) | shares
Options Vested, Weighted-Average Exercise Price per Share (in dollars per share)
Range 2 [Member]
Lower Range of Exercise Price (in dollars per share)	1.64
Upper Range of Exercise Price (in dollars per share)	$ 1.64
Options Outstanding, Number of Shares (in shares) | shares	2,000
Options Outstanding, Weighted-Average Remaining Contractual Life (Year)	9 years 54 days
Options Vested, Number of Shares (in shares) | shares
Options Vested, Weighted-Average Exercise Price per Share (in dollars per share)
Range 3 [Member]
Lower Range of Exercise Price (in dollars per share)	1.80
Upper Range of Exercise Price (in dollars per share)	$ 2
Options Outstanding, Number of Shares (in shares) | shares	578
Options Outstanding, Weighted-Average Remaining Contractual Life (Year)	9 years 222 days
Options Vested, Number of Shares (in shares) | shares	22
Options Vested, Weighted-Average Exercise Price per Share (in dollars per share)	$ 1.83
Range 4 [Member]
Lower Range of Exercise Price (in dollars per share)	3.24
Upper Range of Exercise Price (in dollars per share)	$ 3.99
Options Outstanding, Number of Shares (in shares) | shares	318
Options Outstanding, Weighted-Average Remaining Contractual Life (Year)	8 years 255 days
Options Vested, Number of Shares (in shares) | shares	128
Options Vested, Weighted-Average Exercise Price per Share (in dollars per share)	$ 3.46
Range 5 [Member]
Lower Range of Exercise Price (in dollars per share)	4.32
Upper Range of Exercise Price (in dollars per share)	$ 4.32
Options Outstanding, Number of Shares (in shares) | shares	655
Options Outstanding, Weighted-Average Remaining Contractual Life (Year)	8 years 208 days
Options Vested, Number of Shares (in shares) | shares	233
Options Vested, Weighted-Average Exercise Price per Share (in dollars per share)	$ 4.32
Range 6 [Member]
Lower Range of Exercise Price (in dollars per share)	5.18
Upper Range of Exercise Price (in dollars per share)	$ 6.61
Options Outstanding, Number of Shares (in shares) | shares	754
Options Outstanding, Weighted-Average Remaining Contractual Life (Year)	7 years 193 days
Options Vested, Number of Shares (in shares) | shares	468
Options Vested, Weighted-Average Exercise Price per Share (in dollars per share)	$ 6.25
Range 7 [Member]
Lower Range of Exercise Price (in dollars per share)	6.83
Upper Range of Exercise Price (in dollars per share)	$ 6.83
Options Outstanding, Number of Shares (in shares) | shares	50
Options Outstanding, Weighted-Average Remaining Contractual Life (Year)	7 years 51 days
Options Vested, Number of Shares (in shares) | shares	50
Options Vested, Weighted-Average Exercise Price per Share (in dollars per share)	$ 6.83
Range 8 [Member]
Lower Range of Exercise Price (in dollars per share)	7.20
Upper Range of Exercise Price (in dollars per share)	$ 7.20
Options Outstanding, Number of Shares (in shares) | shares	5
Options Outstanding, Weighted-Average Remaining Contractual Life (Year)	2 years 58 days
Options Vested, Number of Shares (in shares) | shares	5
Options Vested, Weighted-Average Exercise Price per Share (in dollars per share)	$ 7.20
Range 9 [Member]
Lower Range of Exercise Price (in dollars per share)	11.40
Upper Range of Exercise Price (in dollars per share)	$ 11.40
Options Outstanding, Number of Shares (in shares) | shares	5
Options Outstanding, Weighted-Average Remaining Contractual Life (Year)	1 year 233 days
Options Vested, Number of Shares (in shares) | shares	5
Options Vested, Weighted-Average Exercise Price per Share (in dollars per share)	$ 11.40
Range 10 [Member]
Lower Range of Exercise Price (in dollars per share)	18.90
Upper Range of Exercise Price (in dollars per share)	$ 18.90
Options Outstanding, Number of Shares (in shares) | shares	1
Options Outstanding, Weighted-Average Remaining Contractual Life (Year)	317 days
Options Vested, Number of Shares (in shares) | shares	1
Options Vested, Weighted-Average Exercise Price per Share (in dollars per share)	$ 18.90