Fair Value (Differences between Aggregate Fair Value and Aggregate Remaining Contractual Principal Balance Outstanding) (Detail) - JPY (¥) ¥ in Millions	Mar. 31, 2026	Mar. 31, 2025
Fair Value, Option, Quantitative Disclosures [Line Items]
Remaining aggregate contractual amounts outstanding, Financial liabilities	¥ 81,737	¥ 156,302
Fair value	79,698	153,742
Fair value over (under) remaining aggregate contractual amounts outstanding, Financial liabilities	(2,039)	(2,560)
Long-term debt
Fair Value, Option, Quantitative Disclosures [Line Items]
Remaining aggregate contractual amounts outstanding, Financial liabilities	81,737	156,302
Fair value	79,698	153,742
Fair value over (under) remaining aggregate contractual amounts outstanding, Financial liabilities	¥ (2,039)	¥ (2,560)

Aggregate fair value of long-term debt instruments for which the fair value option has been elected.

No definition available.

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- Definition

Remaining aggregate contractual amount of long-term debt instruments for which the fair value option has been elected.

+ References

No definition available.

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- Definition

This item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of long-term debt instruments that have contractual principal amounts and for which the fair value option has been elected.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (d)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-28

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- 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.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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