6. FINANCIAL INSTRUMENTS - Available for sale investments (Details) - USD ($)	6 Months Ended
Sep. 30, 2017	Mar. 31, 2017
Available-for-sale investments
Cost	$ 26,847,000
Fair Value	$ 26,799,000
Other information
Maximum maturity period of investment portfolio	3 years
Deferred tax asset related to unrecognized gains and losses on short-term and long-term investments	$ 16,000	$ 17,000
Short-term investments
Available-for-sale investments
Cost	12,215,000	16,202,000
Gross Unrealized Gains	2,000	10,000
Gross Unrealized Losses	(14,000)	(13,000)
Fair Value	12,203,000	16,199,000
Short-term investments \| State and municipal obligations
Available-for-sale investments
Cost	1,601,000	1,632,000
Gross Unrealized Gains		1,000
Fair Value	1,601,000	1,633,000
Short-term investments \| Corporate notes
Available-for-sale investments
Cost	556,000	557,000
Gross Unrealized Losses	(1,000)	(2,000)
Fair Value	555,000	555,000
Short-term investments \| Certificates of deposits
Available-for-sale investments
Cost	7,000,000	10,000,000
Gross Unrealized Gains	2,000	9,000
Gross Unrealized Losses	(7,000)	(3,000)
Fair Value	6,995,000	10,006,000
Short-term investments \| Foreign government obligations
Available-for-sale investments
Cost	1,053,000	1,001,000
Gross Unrealized Losses	(3,000)	(1,000)
Fair Value	1,050,000	1,000,000
Short-term investments \| Agency bonds
Available-for-sale investments
Cost	2,005,000	3,012,000
Gross Unrealized Losses	(3,000)	(7,000)
Fair Value	2,002,000	3,005,000
Long-term investment
Available-for-sale investments
Cost	14,632,000	12,942,000
Gross Unrealized Gains	2,000	3,000
Gross Unrealized Losses	(38,000)	(47,000)
Fair Value	14,596,000	12,898,000
Long-term investment \| Certificates of deposits
Available-for-sale investments
Cost	10,250,000	7,500,000
Gross Unrealized Gains	1,000	3,000
Gross Unrealized Losses	(35,000)	(39,000)
Fair Value	10,216,000	7,464,000
Long-term investment \| Foreign government obligations
Available-for-sale investments
Cost	4,382,000	5,442,000
Gross Unrealized Gains	1,000
Gross Unrealized Losses	(3,000)	(8,000)
Fair Value	$ 4,380,000	$ 5,434,000

Represents the maximum maturity period of investments.

No definition available.

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- Definition

This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

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- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

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- References

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- Definition

Amount of debt securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 320
-Section 50
-Paragraph 2
-Subparagraph (b)-(g)
-URI http://asc.fasb.org/extlink&oid=75019621&loc=d3e62557-112803

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- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from investments (excludes investments in subsidiaries and equity method investments).

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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