Equity Method Investments (Summary of Equity Method Investments) (Detail) - JPY (¥) ¥ in Millions	Mar. 31, 2026	Mar. 31, 2025
Schedule of Equity Method Investments [Line Items]
Equity method investments	¥ 1,306,312	¥ 1,320,015
Investment in corporate entities [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	868,090	973,795
Investment in real estate joint ventures [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	127,528	137,274
Investment in partnerships and other investments [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	¥ 310,694	¥ 208,946

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

- Definition

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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