Pledged Assets and Collateral (Assets Mortgaged, Pledged, or Otherwise Subject to Lien) (Detail) ¥ in Millions	Mar. 31, 2026 JPY (¥)
Financial Instruments Owned and Pledged as Collateral [Line Items]
Pledged assets	¥ 30,517,532
Trading account securities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Pledged assets	14,349,756
Investment securities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Pledged assets	10,018,070
Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Pledged assets	6,121,133
Other
Financial Instruments Owned and Pledged as Collateral [Line Items]
Pledged assets	¥ 28,573

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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-04(11))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481444/860-30-45-1

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