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Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions		6 Months Ended
	Jan. 05, 2018	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Period for Make Whole Payment		90 days
Make Whole Payment	$ 0.7

X

- Definition

Business Combination, Period for Make Whole Payment

+ References

No definition available.

+ Details

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Namespace Prefix:	amsc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- References

No definition available.

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Namespace Prefix:	us-gaap_
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X

- Definition

Amount of cash outflow, not made soon after acquisition date of business combination, to settle contingent consideration liability exceeding amount recognized at acquisition date. Includes, but is not limited to, measurement period adjustment and less amount paid soon after acquisition date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 17
-Subparagraph (ee)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3367-108585

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