7. FINANCIAL INSTRUMENTS - Unrealized losses and fair value (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Mar. 31, 2019
Fair Value
Less Than 12 Months, Fair Value	$ 6,815	$ 7,365
12 Months or Greater, Fair Value	500	7,974
Total, Fair Value	7,315	15,339
Unrealized Loss
Less Than 12 Months, Unrealized Loss	3	4
12 Months or Greater, Unrealized Loss		26
Total, Unrealized Loss	3	30
Certificates of deposit
Fair Value
Less Than 12 Months, Fair Value		2,998
12 Months or Greater, Fair Value	500	7,974
Total, Fair Value	500	10,972
Unrealized Loss
Less Than 12 Months, Unrealized Loss		2
12 Months or Greater, Unrealized Loss		26
Total, Unrealized Loss		28
Supranational obligations
Fair Value
Less Than 12 Months, Fair Value	2,998	2,866
Total, Fair Value	2,998	2,866
Unrealized Loss
Less Than 12 Months, Unrealized Loss	1	1
Total, Unrealized Loss	1	1
Agency bonds
Fair Value
Less Than 12 Months, Fair Value	3,817	1,501
Total, Fair Value	3,817	1,501
Unrealized Loss
Less Than 12 Months, Unrealized Loss	2	1
Total, Unrealized Loss	$ 2	$ 1