Equity Method Investments - Additional Information (Detail) - JPY (¥) ¥ in Millions	12 Months Ended
Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2024
Schedule of Equity Method Investments [Line Items]
Investment in affiliates, aggregate investment	¥ 110,714	¥ 107,524
Investment in affiliates, market value	112,537	107,466
Investment in affiliates, dividends received	55,535	30,151	¥ 25,820
Investment in affiliates over underlying equity in net assets	¥ 42,600	¥ 127,779
Kansai Airports
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	40.00%	40.00%
DOCOMO Finance, Inc.
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	34.00%	34.00%
Avolon Holdings
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	30.00%	30.00%
TB Investment Limited Partnership
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	20.00%

This element represents the aggregate cost of investments accounted for under the equity method of accounting.

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Difference between amount at which an investment accounted for under the equity method of accounting is carried (reported) on the balance sheet and amount of underlying equity in net assets the reporting Entity has in the investee.

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Amount of distribution received from equity method investee for return on investment, classified as operating activities. Excludes distribution for return of investment, classified as investing activities.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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This item represents the aggregate value of each identified investment accounted for under the equity method of accounting based on the quoted market price for those investments in common stock for which a quoted market price is available.

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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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