Business and Basis of Presentation (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended	12 Months Ended
	Feb. 12, 2020	Mar. 31, 2021	Mar. 31, 2022	Dec. 31, 2020	Dec. 07, 2021	Nov. 09, 2021	Oct. 04, 2021	Aug. 13, 2021	Dec. 23, 2020	Feb. 27, 2020	Feb. 11, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Merger conversion rate (in shares)	0.08289152527
Common stock, shares issued (in shares)	4,171,571	40,531,996	53,379,307								50,325,662
Common stock, forfeited and cancelled (in shares)	682,699
Shares issued under company plans (in shares)	2,461,923	2,543,125	2,879,008	2,320,318								2,473,198
Number of shares (in shares)	15,461		2,657,298								186,535
Conversion price per share on convertible note payable (in dollars per share)	$ 5.12						$ 5.00
Number of common stock shares converted per preferred share (in shares)							3,120,000
Net cash used in operating activities		$ (4,933)	$ (19,736)	$ (14,115)
Proceeds from issuance of common stock		1,000	50,900	36,520
Series 1 Preferred Stock
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common stock, shares issued (in shares)	12,433,953
Convertible preferred stock, shares issued (in shares)	51,680,254										51,680,254
Convertible preferred stock, shares outstanding (in shares)	51,680,254										51,680,254
Conversion of preferred shares in connection with the Reverse Merger (in shares)	12,433,953
Series 2 Preferred Stock
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common stock, shares issued (in shares)	7,499,996
Convertible preferred stock, shares issued (in shares)	38,760,190										38,760,190
Convertible preferred stock, shares outstanding (in shares)	38,760,190										38,760,190
Conversion of stock (in shares)	7,499,996
Series 3 Preferred Stock
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common stock, shares issued (in shares)	4,000,000
Convertible preferred stock, shares issued (in shares)	31,850,304										31,850,304
Convertible preferred stock, shares outstanding (in shares)	31,850,304										31,850,304
Conversion of stock (in shares)	4,000,000
Yaskawa
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Conversion price per share on convertible note payable (in dollars per share)	$ 5.12						$ 5.00
Yaskawa Note
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accrued interest on promissory note		$ 523	0	$ 486
Yaskawa Note | Yaskawa
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Principal and unpaid interest of convertible note							$ 15,600
Principal amount of long term loan facility							15,000
Accrued interest on promissory note							$ 600
Number of common stock shares converted per preferred share (in shares)							3,120,000
Transphorm Technology 2007 Stock Plan and 2015 Equity Incentive Plan
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Shares issued under company plans (in shares)	29,703,285
Former Holders of Tranphorm Technology's Common Stock
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Common stock, shares issued (in shares)	4,171,571
Conversion of preferred shares in connection with the Reverse Merger (in shares)	28,105,520
Private Placement
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Price per share (in dollars per share)		$ 4.00			$ 7.71	$ 5.00		$ 5.00	$ 3.00	$ 4.00
Proceeds from issuance of common stock			$ 50,900
Common Stock
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Price per share (in dollars per share)	$ 4.00
Conversion of preferred shares in connection with the Reverse Merger (in shares)			3,120,000	23,933,949