v3.26.1

Summary of Significant Accounting Policies - Additional information (Details) $ in Thousands	12 Months Ended
	Mar. 31, 2026 USD ($) segment	Mar. 31, 2025 USD ($)	Mar. 31, 2024
Cash and Cash Equivalents [Line Items]
Money market funds \| $	$ 902,110	$ 713,971
Estimated useful life (in years)	3 years
Expected dividend yield	0.00%	0.00%	0.00%
Number of reportable segments \| segment	1
Number of operating segments \| segment	1
Money Market Funds \| Fair Value, Inputs, Level 1
Cash and Cash Equivalents [Line Items]
Money market funds \| $	$ 877,800	$ 687,600

Amount of cash and cash equivalent. Cash includes, but is not limited to, currency on hand, demand deposit with financial institution, and account with general characteristic of demand deposit. Cash equivalent includes, but is not limited to, short-term, highly liquid investment that is both readily convertible to known amount of cash and so near maturity that it presents insignificant risk of change in value because of change in interest rate.

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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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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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Immunovant, Inc. 10-K