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Minority Investments - Additional Information (Detail) (USD $) | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2014 | Mar. 31, 2014 | Dec. 31, 2014 | Mar. 31, 2014
Tres Amigas |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |
Number of commonly interconnected power grids |  |  | 3 amsc_EquityMethodInvestmentsNumberOfCommonlyInterconnectedPowerGrids / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_TresAmigasMember |
Equity method investment, aggregate cost |  |  | $ 5,400,000 us-gaap_EquityMethodInvestmentAggregateCost / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_TresAmigasMember |
Percentage of ownership interest hold |  |  | 26.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_TresAmigasMember |
Blade Dynamics Ltd. |  |  |  |
Schedule Of Equity Method Investments [Line Items] |  |  |  |
Cost method investment, original cost |  |  | 8,000,000 us-gaap_CostMethodInvestmentsOriginalCost / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_BladeDynamicsLtdMember |
Percentage of ownership interest hold |  |  | 12.00%us-gaap_MinorityInterestOwnershipPercentageByParent / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_BladeDynamicsLtdMember |
Impairment charge on investment | $ 3,500,000 us-gaap_ImpairmentOfInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_BladeDynamicsLtdMember | $ 1,300,000 us-gaap_ImpairmentOfInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_BladeDynamicsLtdMember | $ 3,464,000 us-gaap_ImpairmentOfInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_BladeDynamicsLtdMember | $ 1,300,000 us-gaap_ImpairmentOfInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_BladeDynamicsLtdMember

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- Definition Equity method investments, number of commonly interconnected power grids. + References No definition available. + Details
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Namespace Prefix: | amsc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- Definition Original amount of cost-method investments at the acquisition date. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | debit
Period Type: | instant

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- Definition This element represents the aggregate cost of investments accounted for under the equity method of accounting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 12 -Article 5 + Details
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Balance Type: | debit
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- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 + Details
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- Definition The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 35 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e25351-111560 + Details
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- Definition The parent entity's interest in net assets of the subsidiary, expressed as a percentage. + References No definition available. + Details
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- Details
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- Details
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- Details
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