Condensed Financial Information of Deswell Industries, Inc. (Details) $ in Thousands, ¥ in Millions	Mar. 31, 2025 USD ($)	Mar. 31, 2025 CNY (¥)	Mar. 31, 2024 USD ($)	Mar. 31, 2024 CNY (¥)
Condensed Financial Information of Deswell Industries, Inc. [Abstract]
Net assets of subsidiaries restricted amount	$ 51,984	¥ 376	$ 52,697	¥ 376

The amount of net assets recorded by subsidiaries restricted from transfer to the parent. The amounts restricted include paid-in capital and statutory reserves, as determined pursuant to PRC generally accepted accounting principles.

No definition available.

Name:	dswl_NetAssetsOfSubsidiariesRestrictedFromTransferToParentCompany
Namespace Prefix:	dswl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant