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Minority Investments - Schedule of Net Investment Activity (Detail) (USD $) In Thousands, unless otherwise specified | 3 Months Ended | 9 Months Ended | 3 Months Ended | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2014 | Dec. 31, 2013 | Sep. 30, 2014 | Mar. 31, 2014 | Mar. 31, 2014
Schedule Of Results Related To Equity Accounted Investees [Line Items] |  |  |  |  |  |  |
Minority interest in net losses |  |  | $ (644)us-gaap_GainLossOnInvestments | $ (789)us-gaap_GainLossOnInvestments |  |  |
Net foreign exchange rate impact | (209)us-gaap_OtherNonoperatingIncomeExpense | (341)us-gaap_OtherNonoperatingIncomeExpense | 379 us-gaap_OtherNonoperatingIncomeExpense | (908)us-gaap_OtherNonoperatingIncomeExpense |  |  |
Tres Amigas |  |  |  |  |  |  |
Schedule Of Results Related To Equity Accounted Investees [Line Items] |  |  |  |  |  |  |
Beginning Balance |  |  | 1,845 amsc_NetInvestmentActivityInBusinessAcquisitions / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_TresAmigasMember |  |  |  |
Minority interest in net losses |  |  | (644)us-gaap_GainLossOnInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_TresAmigasMember |  |  |  |
Ending Balance | 1,201 amsc_NetInvestmentActivityInBusinessAcquisitions / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_TresAmigasMember |  | 1,201 amsc_NetInvestmentActivityInBusinessAcquisitions / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_TresAmigasMember |  |  |  |
Blade Dynamics Ltd. |  |  |  |  |  |  |
Schedule Of Results Related To Equity Accounted Investees [Line Items] |  |  |  |  |  |  |
Beginning Balance |  |  | 3,690 amsc_NetInvestmentActivityInBusinessAcquisitions / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_BladeDynamicsLtdMember |  |  |  |
Net foreign exchange rate impact |  |  | (226)us-gaap_OtherNonoperatingIncomeExpense / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_BladeDynamicsLtdMember |  |  |  |
Impairment |  |  | $ (3,464)us-gaap_ImpairmentOfInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_BladeDynamicsLtdMember |  | $ (3,500)us-gaap_ImpairmentOfInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_BladeDynamicsLtdMember | $ (1,300)us-gaap_ImpairmentOfInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_BladeDynamicsLtdMember | $ (1,300)us-gaap_ImpairmentOfInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_BladeDynamicsLtdMember

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- Definition This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains (losses) realized during the period from the sale of investments accounted for under the cost method of accounting and losses recognized for other than temporary impairments (OTTI) of the subject investments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -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 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.7(c),9(a)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27405-111563 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (c)-(e) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Article 5 + Details
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- Definition The net amount of other income and expense amounts, the components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating income (expense) recognized for the period. Such amounts may include: (a) dividends, (b) interest on securities, (c) net gains or losses on securities, (d) unusual costs, (e) gains or losses on foreign exchange transactions, and (f) miscellaneous other income and expense items. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 9 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.9) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 + Details
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