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Stock-Based Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified | 9 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013
Stock Options |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |
Stock options granted in period | 1,000,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | 831,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember
Unrecognized compensation cost for unvested employee stock-based compensation awards outstanding, net of forfeitures | $ 1.5 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Weighted-average period over which unrecognized compensation expense is expected to be recognized (years) | 3 years |
Stock Options | Minimum |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |
Vesting period, in years | 3 years |
Stock Options | Maximum |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |
Vesting period, in years | 5 years |
Restricted Stock |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |
Restricted stock granted | 3,243,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
Vesting period, in years | 3 years |
Unrecognized compensation cost for unvested employee stock-based compensation awards outstanding, net of forfeitures | $ 3.7 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember |
Weighted-average period over which unrecognized compensation expense is expected to be recognized (years) | 1 year 4 months 24 days |
Time-Based Restricted Stock |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |
Restricted stock granted |  | 1,307,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = amsc_TimeBasedRestrictedStockMember
Performance-Based Restricted Stock |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |
Restricted stock granted |  | 362,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = amsc_PerformanceBasedRestrictedStockMember
Common Stock |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |
Stock options granted in period |  | 212,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod / us-gaap_StatementEquityComponentsAxis = us-gaap_CommonStockMember

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- Definition Unrecognized cost of unvested share-based compensation awards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Details
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- Definition Net number of share options (or share units) granted during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Details
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Data Type: | na
Balance Type: |
Period Type: |

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- Details
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- Details
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- Details
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