Parent Company Only Financial Information (Narrative) (Detail) - BK and TB - JPY (¥) ¥ in Billions	Mar. 31, 2024	Mar. 31, 2023
Companies Act
Parent Company Only Financial Information [Line Items]
Unrestricted amount of retained earnings that are in excess of the level required under the statutory reserve requirements	¥ 6,159	¥ 5,837
Banking Law and Related Regulations
Parent Company Only Financial Information [Line Items]
Percentage limitation of loans or credits to the parent company over the banking subsidiary's consolidated total capital	15.00%
Restricted amount of net assets of consolidated subsidiaries as to payment of cash dividends and loans to the parent company	¥ 6,441	¥ 5,352

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
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Subsection 04
-Paragraph a
-Publisher SEC

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 5
-Subsection 04
-Paragraph c
-Subparagraph Schedule I
-Publisher SEC

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 7
-Subsection 05
-Paragraph c
-Subparagraph Schedule II
-Publisher SEC

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 9
-Subsection 06
-Publisher SEC

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04(a))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-3

Reference 6: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 810
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481231/810-10-45-11

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