Warrant instruments, fair value disclosure.

No definition available.

Name:	amsc_WarrantInstrumentsFairValueDisclosure
Namespace Prefix:	amsc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Expected dividends to be paid to holders of the underlying shares or financial instruments (expressed as a percentage of the share or instrument's price).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueAssumptionsExpectedDividendRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period the instrument, asset or liability is expected to be outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_FairValueAssumptionsExpectedTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Measure of dispersion, in percentage terms (for instance, the standard deviation or variance), for a given stock price.

+ References

+ Details

Name:	us-gaap_FairValueAssumptionsExpectedVolatilityRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Risk-free interest rate assumption used in valuing an instrument.

+ References

+ Details

Name:	us-gaap_FairValueAssumptionsRiskFreeInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=amsc_NovemberTwoThousandFourteenWarrantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=amsc_SeniorConvertibleNoteWarrantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=amsc_SeniorSecuredTermLoanFirstWarrantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=amsc_SeniorSecuredTermLoanNewWarrantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ClassOfWarrantOrRightAxis=amsc_SeniorSecuredTermLoanSecondWarrantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Warrants and Derivative Liabilities - Schedule of Assumptions Used to Calculate the Fair Value of Warrants (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended								0 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Oct. 09, 2013	Dec. 19, 2014	Nov. 15, 2013	Nov. 13, 2014
Derivative [Line Items]
Risk-free interest rate	0.12%	0.10%	0.21%	0.20%
Expected annual dividend yield	16.50%	15.50%	16.70%	16.50%
Expected volatility	68.63%	66.26%	65.80%	66.91%
Term (years)	9 months	1 year	1 year 3 months 4 days	1 year 6 months 4 days
Senior Convertible Note Warrant
Derivative [Line Items]
Risk-free interest rate	1.17%	1.02%	1.13%	0.67%	1.00%	1.07%	0.98%	1.11%
Expected volatility	75.60%	71.98%	71.90%	71.74%	72.38%	76.20%	83.50%	80.99%
Term (years)	3 years 9 months 4 days	4 years 4 days	4 years 3 months 7 days	4 years 6 months 4 days	2 years 9 months 4 days	3 years 4 days	3 years 3 months 4 days	3 years 6 months 4 days
Fair value	2.2	2.5	3.0	3.4	$ 0.5	$ 1.5	$ 2.3	$ 2.2
Senior Convertible Note Warrant \| Post Modification
Derivative [Line Items]
Risk-free interest rate									1.05%
Expected volatility									71.45%
Term (years)									3 years 11 months 27 days
Fair value									3.2
Senior Convertible Note Warrant \| Pre Modification
Derivative [Line Items]
Risk-free interest rate									1.05%
Expected volatility									71.45%
Term (years)									3 years 11 months 27 days
Fair value									2.2
Senior Secured Term Loan First Warrant
Derivative [Line Items]
Risk-free interest rate	1.24%	1.09%	1.20%	0.70%		1.13%	1.04%	1.18%		1.10%
Expected volatility	74.79%	72.10%	72.30%	72.01%		78.30%	82.75%	80.73%		67.01%
Term (years)	3 years 11 months 5 days	4 years 2 months 5 days	4 years 5 months 5 days	4 years 8 months 5 days	0 years	3 years 2 months 5 days	3 years 5 months 5 days	3 years 8 months 5 days		2 years 11 months 16 days
Fair value	0.1	0.2	0.2	0.2	0	0.1	0.1	0.1		0.1
Senior Secured Term Loan First Warrant \| Post Modification
Derivative [Line Items]
Risk-free interest rate											1.00%
Expected volatility											72.64%
Term (years)											4 years 18 days
Fair value											0.1
Senior Secured Term Loan First Warrant \| Pre Modification
Derivative [Line Items]
Risk-free interest rate											1.00%
Expected volatility											72.64%
Term (years)											4 years 18 days
Fair value											0.1
Senior Secured Term Loan Second Warrant
Derivative [Line Items]
Risk-free interest rate	1.89%					1.65%	1.57%	1.76%		1.65%	1.55%
Expected volatility	80.37%					78.10%	80.00%	79.73%		71.82%	76.97%
Term (years)	5 years 4 months 13 days				0 years	4 years 7 months 13 days	4 years 10 months 13 days	5 years 1 month 13 days		4 years 4 months 28 days	5 years 5 months 27 days
Fair value	0.3				0	0.2	0.3	0.3		0.1	0.3
Senior Secured Term Loan New Warrant
Derivative [Line Items]
Risk-free interest rate					1.73%					1.74%
Expected volatility					77.43%					70.26%
Term (years)					5 years 6 months					5 years 6 months 11 days
Fair value					0.2					0.2
November 2014 Warrant
Derivative [Line Items]
Risk-free interest rate					1.61%							1.64%
Expected volatility					78.00%							72.86%
Term (years)					4 years 10 months 13 days							5 years
Fair value					$ 3.2							$ 4.3