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v2.4.1.9

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified | 12 Months Ended
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Mar. 31, 2015 | Mar. 31, 2014 | Mar. 31, 2013
Inventory reserve | $ 1.4 us-gaap_InventoryValuationReserves | $ 0.3 us-gaap_InventoryValuationReserves |
Benefit to cost of revenues | 8.0 amsc_CostOfRevenuesBenefitInventoriesPreviouslyWrittenDown | 4.3 amsc_CostOfRevenuesBenefitInventoriesPreviouslyWrittenDown | 2.1 amsc_CostOfRevenuesBenefitInventoriesPreviouslyWrittenDown
Impairment charge |  | 0 us-gaap_AssetImpairmentCharges | 5.0 us-gaap_AssetImpairmentCharges
Payments received from customers | 0 us-gaap_Revenues | 3.7 us-gaap_Revenues | 3.4 us-gaap_Revenues
Percentage of tax benefit likely to be realized upon ultimate settlement | 50.00%amsc_PercentageOfTaxBenefitLikelyToBeRealizedUponUltimateSettlement |  |
Repatriated amount | 1.2 us-gaap_ForeignEarningsRepatriated |  |
Common equivalent shares not included in the calculation of diluted EPS | 1,567,352 us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount | 643,158 us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount | 1,072,584 us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Net foreign currency transaction and hedging gains (losses) | 2.8 us-gaap_ForeignCurrencyTransactionGainLossBeforeTax | 0.1 us-gaap_ForeignCurrencyTransactionGainLossBeforeTax | 1.0 us-gaap_ForeignCurrencyTransactionGainLossBeforeTax
Loss contingency accrual |  |  | 1.8 us-gaap_LossContingencyAccrualAtCarryingValue
Ghodawat Energy Pvt Ltd |  |  |
Reversed legal expenses | 2.2 us-gaap_LegalFees / dei_LegalEntityAxis = amsc_GhodawatEnergyPvtLtdMember |  |
Foreign Earnings Repatriated |  |  |
Federal and state deferred tax liability | 0.4 us-gaap_DeferredTaxLiabilitiesCurrent / us-gaap_IncomeTaxAuthorityAxis = amsc_ForeignEarningsRepatriatedMember |  |
Blade Dynamics Ltd |  |  |
Impairment charge | $ 3.5 us-gaap_AssetImpairmentCharges / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_BladeDynamicsLtdMember | $ 1.3 us-gaap_AssetImpairmentCharges / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = amsc_BladeDynamicsLtdMember |
Maximum |  |  |
Warranty period | 3 years |  |
Minimum |  |  |
Warranty period | 1 year |  |
Credit Concentration Risk | Accounts Receivable | Inox Wind Limited |  |  |
Risk percentage | 56.00%us-gaap_ConcentrationRiskPercentage1 / us-gaap_ConcentrationRiskByBenchmarkAxis = us-gaap_AccountsReceivableMember / us-gaap_ConcentrationRiskByTypeAxis = us-gaap_CreditConcentrationRiskMember / us-gaap_MajorCustomersAxis = amsc_InoxWindLimitedMember | 20.00%us-gaap_ConcentrationRiskPercentage1 / us-gaap_ConcentrationRiskByBenchmarkAxis = us-gaap_AccountsReceivableMember / us-gaap_ConcentrationRiskByTypeAxis = us-gaap_CreditConcentrationRiskMember / us-gaap_MajorCustomersAxis = amsc_InoxWindLimitedMember |
Credit Concentration Risk | Accounts Receivable | Inox Wind Limited | Maximum |  |  |
Risk percentage | 56.00%us-gaap_ConcentrationRiskPercentage1 / us-gaap_ConcentrationRiskByBenchmarkAxis = us-gaap_AccountsReceivableMember / us-gaap_ConcentrationRiskByTypeAxis = us-gaap_CreditConcentrationRiskMember / us-gaap_MajorCustomersAxis = amsc_InoxWindLimitedMember / us-gaap_RangeAxis = us-gaap_MaximumMember |  |
Credit Concentration Risk | Accounts Receivable | Inox Wind Limited | Minimum |  |  |
Risk percentage | 10.00%us-gaap_ConcentrationRiskPercentage1 / us-gaap_ConcentrationRiskByBenchmarkAxis = us-gaap_AccountsReceivableMember / us-gaap_ConcentrationRiskByTypeAxis = us-gaap_CreditConcentrationRiskMember / us-gaap_MajorCustomersAxis = amsc_InoxWindLimitedMember / us-gaap_RangeAxis = us-gaap_MinimumMember |  |
Credit Concentration Risk | Accounts Receivable | CG Power Solutions UK Ltd |  |  |
Risk percentage |  | 14.00%us-gaap_ConcentrationRiskPercentage1 / us-gaap_ConcentrationRiskByBenchmarkAxis = us-gaap_AccountsReceivableMember / us-gaap_ConcentrationRiskByTypeAxis = us-gaap_CreditConcentrationRiskMember / us-gaap_MajorCustomersAxis = amsc_CGPowerSolutionsUKLtdMember |
Credit Concentration Risk | Accounts Receivable | JINGCHENG New Energy |  |  |
Risk percentage |  | 13.00%us-gaap_ConcentrationRiskPercentage1 / us-gaap_ConcentrationRiskByBenchmarkAxis = us-gaap_AccountsReceivableMember / us-gaap_ConcentrationRiskByTypeAxis = us-gaap_CreditConcentrationRiskMember / us-gaap_MajorCustomersAxis = amsc_JINGCHENGNewEnergyMember |

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