7. FINANCIAL INSTRUMENTS - Available-for-sale investments (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 31, 2019
Available-for-sale investments
Cost	$ 25,475
Total	25,546
Short-term investments
Available-for-sale investments
Cost	18,262	$ 19,367
Gross Unrealized Gains	26	4
Gross Unrealized Losses	(6)	(25)
Total	18,282	19,346
Short-term investments | Agency bonds
Available-for-sale investments
Cost	1,501
Gross Unrealized Gains	5
Total	1,506
Short-term investments | Supranational obligations
Available-for-sale investments
Cost	1,261	2,867
Gross Unrealized Gains	1
Gross Unrealized Losses		(1)
Total	1,262	2,866
Short-term investments | Certificates of deposit
Available-for-sale investments
Cost	15,500	16,500
Gross Unrealized Gains	20	4
Gross Unrealized Losses	(6)	(24)
Total	15,514	16,480
Long-term investment
Available-for-sale investments
Cost	7,213	8,968
Gross Unrealized Gains	53	34
Gross Unrealized Losses	(2)	(5)
Total	7,264	8,997
Long-term investment | Agency bonds
Available-for-sale investments
Cost	1,473	2,968
Gross Unrealized Gains	17	11
Gross Unrealized Losses		(1)
Total	1,490	2,978
Long-term investment | Certificates of deposit
Available-for-sale investments
Cost	5,740	6,000
Gross Unrealized Gains	36	23
Gross Unrealized Losses	(2)	(4)
Total	$ 5,774	$ 6,019