Common Stock, Forfeited And Cancelled

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Common Stock, Merger Conversion Rate Of Shares

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Number of warrants or rights outstanding.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The number of new shares issued in the conversion of stock in a noncash (or part noncash) transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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The price per share of the conversion feature embedded in the debt instrument.

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The number of equity instruments that the holder of the debt instrument would receive if the debt was converted to equity.

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Amount of interest payable on debt, including, but not limited to, trade payables.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The cash inflow from the additional capital contribution to the entity.

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Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

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Number of options outstanding, including both vested and non-vested options.

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Number of shares issued during the period as a result of the conversion of convertible securities.

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The number of securities classified as temporary equity that have been sold (or granted) to the entity's shareholders. Securities issued include securities outstanding and securities held in treasury. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

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The number of securities classified as temporary equity that have been issued and are held by the entity's shareholders. Securities outstanding equals securities issued minus securities held in treasury. Temporary equity is a security with redemption features that are outside the control of the issuer, is not classified as an asset or liability in conformity with GAAP, and is not mandatorily redeemable. Includes any type of security that is redeemable at a fixed or determinable price or on a fixed or determinable date or dates, is redeemable at the option of the holder, or has conditions for redemption which are not solely within the control of the issuer. If convertible, the issuer does not control the actions or events necessary to issue the maximum number of shares that could be required to be delivered under the conversion option if the holder exercises the option to convert the stock to another class of equity. If the security is a warrant or a rights issue, the warrant or rights issue is considered to be temporary equity if the issuer cannot demonstrate that it would be able to deliver upon the exercise of the option by the holder in all cases. Includes stock with put option held by ESOP and stock redeemable by holder only in the event of a change in control of the issuer.

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Business and Basis of Presentation (Details) - USD ($)		1 Months Ended		12 Months Ended
Business and Basis of Presentation (Details) - USD ($)	Feb. 12, 2020	Dec. 31, 2020	Feb. 29, 2020	Dec. 31, 2020	Dec. 31, 2019	Feb. 11, 2020	Jan. 01, 2020	Dec. 31, 2018
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Merger conversion rate (in shares)	0.08289152527
Common stock, shares issued (in shares)	4,171,571	40,278,496		40,278,496	4,220,998	50,325,662
Common stock, forfeited and cancelled (in shares)	682,699
Shares issued under company plans (in shares)	2,461,923	2,320,318		2,320,318	2,473,198		2,473,198	2,377,180
Number of shares (in shares)	15,461	159,415		159,415		186,535
Conversion price per share on convertible note payable (in dollars per share)	$ 5.12
Maximum number of shares of common stock issuable (in shares)	3,076,171
Proceeds from issuance of common stock, net of $3.1 million offering cost		$ 13,600,000	$ 19,700,000	$ 33,387,000	$ 0
Yaskawa Note
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Maximum number of shares of common stock issuable (in shares)	3,076,171
Principal amount of long term loan facility		15,000,000.0		15,000,000.0
Accrued interest on promissory note		$ 486,000		$ 486,000	$ 336,000
Transphorm Technology 2007 Stock Plan and 2015 Equity Incentive Plan
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Shares issued under company plans (in shares)	29,703,285
Series 1 Preferred Stock
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Convertible preferred stock, shares issued (in shares)	51,680,254
Convertible preferred stock, shares outstanding (in shares)	51,680,254
Share conversion in connection with the Merger (in shares)	12,433,953
Series 2 Preferred Stock
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Convertible preferred stock, shares issued (in shares)	38,760,190
Convertible preferred stock, shares outstanding (in shares)	38,760,190
Conversion of stock (in shares)	7,499,996
Series 3 Preferred Stock
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Convertible preferred stock, shares issued (in shares)	31,850,304
Convertible preferred stock, shares outstanding (in shares)	31,850,304
Conversion of stock (in shares)	4,000,000
Common Stock
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Price per share (in dollars per share)	$ 4.00
Share conversion in connection with the Merger (in shares)				23,933,949
Transphorm Technology
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Share conversion in connection with the Merger (in shares)	28,105,520