7. FINANCIAL INSTRUMENTS - Unrealized losses and fair value (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 31, 2019
Fair Value
Less Than 12 Months, Fair Value		$ 7,365
12 Months or Greater, Fair Value	$ 5,992	7,974
Total, Fair Value	5,992	15,339
Unrealized Loss
Less Than 12 Months, Unrealized Loss		4
12 Months or Greater, Unrealized Loss	8	26
Total, Unrealized Loss	8	30
Certificates of deposit
Fair Value
Less Than 12 Months, Fair Value		2,998
12 Months or Greater, Fair Value	5,992	7,974
Total, Fair Value	5,992	10,972
Unrealized Loss
Less Than 12 Months, Unrealized Loss		2
12 Months or Greater, Unrealized Loss	8	26
Total, Unrealized Loss	$ 8	28
Supranational obligations
Fair Value
Less Than 12 Months, Fair Value		2,866
Total, Fair Value		2,866
Unrealized Loss
Less Than 12 Months, Unrealized Loss		1
Total, Unrealized Loss		1
Agency bonds
Fair Value
Less Than 12 Months, Fair Value		1,501
Total, Fair Value		1,501
Unrealized Loss
Less Than 12 Months, Unrealized Loss		1
Total, Unrealized Loss		$ 1