Short-term investments (Details) - Short-term investments - USD ($) $ in Thousands	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Short-term investments
Amortized cost	$ 108,732	$ 109,092
Gross unrealized gains	388	19
Gross unrealized losses	(65)	(4)
Fair value	109,055	109,107
Commercial paper
Short-term investments
Amortized cost	21,818	46,687
Gross unrealized gains	66	2
Gross unrealized losses		(2)
Fair value	21,884	46,687
US Government Agency bonds
Short-term investments
Amortized cost	15,217	15,889
Gross unrealized gains	78	4
Fair value	15,295	15,893
US Treasury bonds
Short-term investments
Amortized cost	35,590	38,047
Gross unrealized gains	220	13
Fair value	35,810	38,060
Corporate debt securities
Short-term investments
Amortized cost	36,107	8,469
Gross unrealized gains	24
Gross unrealized losses	(65)	(2)
Fair value	$ 36,066	$ 8,467

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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This item represents the cost of debt and equity 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

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- Definition

Amount of unrealized gain before deducting unrealized loss on investments in debt and equity securities classified as available-for-sale securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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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.

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