Commitments and Contingencies	3 Months Ended
Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Contingencies From time to time, the Company is involved in legal and administrative proceedings and claims of various types. The Company records a liability in its consolidated financial statements for these matters when a loss is known or considered probable and the amount can be reasonably estimated. The Company reviews these estimates each accounting period as additional information is known and adjusts the loss provision when appropriate. If a matter is both probable to result in a liability and the amounts of loss can be reasonably estimated, the Company estimates and discloses the possible loss or range of loss to the extent necessary to make the consolidated financial statements not misleading. If the loss is not probable or cannot be reasonably estimated, a liability is not recorded in its consolidated financial statements. On July 3, 2018, the Company, AMSC China and AMSC Austria entered into the Settlement Agreement with Sinovel. The Settlement Agreement settles the litigation and arbitration proceedings between the Company and Sinovel listed on Schedule 2 of the Settlement Agreement (the “Proceedings”), and any other civil claims, counterclaims, causes of action, rights and obligations directly or indirectly relating to the subject matters of the Proceedings and the contracts between the Company and Sinovel listed on Schedules 1 and 4 of the Settlement Agreement (the “Contracts”), subject to the exception described in Section 1.1 of the Settlement Agreement. The Settlement Agreement was filed as Exhibit 10.1 to the Company’s Form 8-K filed with the Securities and Exchange Commission on July 9, 2018. Under the terms of the Settlement Agreement, Sinovel has agreed to pay AMSC China an aggregate cash amount in Renminbi (RMB) equivalent to $57.5 million, consisting of two installments. Sinovel paid the first installment of $32.5 million on July 4, 2018, and has agreed to pay the second installment of $25.0 million (the “Second Payment”) within ten (10) months after the U.S. District Court for the Western District of Wisconsin (the “District Court”) delivers the first sentence against Sinovel in the criminal case entitled United States v. Sinovel Wind Co., Ltd., Case Number 3:13-cr-00084-jdp. On July 6, 2018, the District Court delivered such sentence, and therefore the Second Payment is due by May 6, 2019 (the “Second Payment Due Date”). Mr. Wenyuan Wei, former Sinovel chairman and a current Sinovel shareholder, has delivered a letter of guarantee (the “Guarantee”) to the Company for the Second Payment should Sinovel fail to make such payment by the Second Payment Due Date. In addition, pursuant to the terms of the Settlement Agreement, the Company and AMSC Austria have granted Sinovel a non-exclusive license for certain AMSC intellectual property to be used solely in Sinovel’s doubly fed wind turbines (the “License”). AMSC has agreed not to sue Sinovel, Sinovel’s power converter suppliers or Sinovel’s customers for use of the technology covered by the License. In the event that Sinovel or Mr. Wei does not make the Second Payment by the Second Payment Due Date, the Settlement Agreement provides that the License will terminate. The Company and Sinovel have submitted withdrawal applications to terminate the Proceedings to the relevant Chinese courts and the Beijing Arbitration Commission. Subject to the Company and Sinovel complying with the terms of the Settlement Agreement, the Company and Sinovel have agreed not to re-institute any of the Proceedings. In addition, the Company and Sinovel have agreed to a mutual release and covenant not to sue covering all subject matters of the Proceedings and Contracts, effective upon the completion of the Second Payment. Other The Company enters into long-term construction contracts with customers that require the Company to obtain performance bonds. The Company is required to deposit an amount equivalent to some or all the face amount of the performance bonds into an escrow account until the termination of the bond. When the performance conditions are met, amounts deposited as collateral for the performance bonds are returned to the Company. In addition, the Company has various contractual arrangements in which minimum quantities of goods or services have been committed to be purchased on an annual basis. As of June 30, 2018, the Company had $0.2 million of restricted cash included in long-term assets. These amounts included in restricted cash primarily represent deposits to secure letters of credit for various supply contracts. These deposits are held in interest bearing accounts.

Commitments and Contingencies

Legal Contingencies

From time to time, the Company is involved in legal and administrative proceedings and claims of various types. The Company records a liability in its consolidated financial statements for these matters when a loss is known or considered probable and the amount can be reasonably estimated. The Company reviews these estimates each accounting period as additional information is known and adjusts the loss provision when appropriate. If a matter is both probable to result in a liability and the amounts of loss can be reasonably estimated, the Company estimates and discloses the possible loss or range of loss to the extent necessary to make the consolidated financial statements not misleading. If the loss is not probable or cannot be reasonably estimated, a liability is not recorded in its consolidated financial statements.

On July 3, 2018, the Company, AMSC China and AMSC Austria entered into the Settlement Agreement with Sinovel. The Settlement Agreement settles the litigation and arbitration proceedings between the Company and Sinovel listed on Schedule 2 of the Settlement Agreement (the “Proceedings”), and any other civil claims, counterclaims, causes of action, rights and obligations directly or indirectly relating to the subject matters of the Proceedings and the contracts between the Company and Sinovel listed on Schedules 1 and 4 of the Settlement Agreement (the “Contracts”), subject to the exception described in Section 1.1 of the Settlement Agreement. The Settlement Agreement was filed as Exhibit 10.1 to the Company’s Form 8-K filed with the Securities and Exchange Commission on July 9, 2018.

Under the terms of the Settlement Agreement, Sinovel has agreed to pay AMSC China an aggregate cash amount in Renminbi (RMB) equivalent to $57.5 million, consisting of two installments. Sinovel paid the first installment of $32.5 million on July 4, 2018, and has agreed to pay the second installment of $25.0 million (the “Second Payment”) within ten (10) months after the U.S. District Court for the Western District of Wisconsin (the “District Court”) delivers the first sentence against Sinovel in the criminal case entitled United States v. Sinovel Wind Co., Ltd., Case Number 3:13-cr-00084-jdp. On July 6, 2018, the District Court delivered such sentence, and therefore the Second Payment is due by May 6, 2019 (the “Second Payment Due Date”). Mr. Wenyuan Wei, former Sinovel chairman and a current Sinovel shareholder, has delivered a letter of guarantee (the “Guarantee”) to the Company for the Second Payment should Sinovel fail to make such payment by the Second Payment Due Date.

In addition, pursuant to the terms of the Settlement Agreement, the Company and AMSC Austria have granted Sinovel a non-exclusive license for certain AMSC intellectual property to be used solely in Sinovel’s doubly fed wind turbines (the “License”). AMSC has agreed not to sue Sinovel, Sinovel’s power converter suppliers or Sinovel’s customers for use of the technology covered by the License. In the event that Sinovel or Mr. Wei does not make the Second Payment by the Second Payment Due Date, the Settlement Agreement provides that the License will terminate.

The Company and Sinovel have submitted withdrawal applications to terminate the Proceedings to the relevant Chinese courts and the Beijing Arbitration Commission. Subject to the Company and Sinovel complying with the terms of the Settlement Agreement, the Company and Sinovel have agreed not to re-institute any of the Proceedings. In addition, the Company and Sinovel have agreed to a mutual release and covenant not to sue covering all subject matters of the Proceedings and Contracts, effective upon the completion of the Second Payment.

Other

The Company enters into long-term construction contracts with customers that require the Company to obtain performance bonds. The Company is required to deposit an amount equivalent to some or all the face amount of the performance bonds into an escrow account until the termination of the bond. When the performance conditions are met, amounts deposited as collateral for the performance bonds are returned to the Company. In addition, the Company has various contractual arrangements in which minimum quantities of goods or services have been committed to be purchased on an annual basis.

As of June 30, 2018, the Company had $0.2 million of restricted cash included in long-term assets. These amounts included in restricted cash primarily represent deposits to secure letters of credit for various supply contracts. These deposits are held in interest bearing accounts.