Loans and Allowance for Credit Losses (Nonaccrual Status of Loans by Class) (Detail) - JPY (¥) ¥ in Millions	12 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual loans	¥ 1,005,133	¥ 1,184,829
Nonaccrual loans not requiring an allowance for credit losses	172,152	201,166
Recognized Interest Income	22,763	19,943
Loans held for sale placed on nonaccrual status	9,205	7,946
Commercial \| Domestic
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual loans	401,836	633,768
Nonaccrual loans not requiring an allowance for credit losses	99,657	109,919
Recognized Interest Income	5,409	6,532
Commercial \| Foreign
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual loans	246,675	224,566
Nonaccrual loans not requiring an allowance for credit losses	65,242	84,837
Recognized Interest Income	5,918	4,734
Residential
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual loans	47,910	56,175
Nonaccrual loans not requiring an allowance for credit losses	3,962	3,579
Recognized Interest Income	1,052	811
Card
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual loans	67,159	62,578
Nonaccrual loans not requiring an allowance for credit losses	0	0
Recognized Interest Income	17	25
MUAH
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual loans		15,349
Nonaccrual loans not requiring an allowance for credit losses		0
Recognized Interest Income		77
Krungsri
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual loans	211,705	165,775
Nonaccrual loans not requiring an allowance for credit losses	3,286	2,824
Recognized Interest Income	6,482	4,076
Other
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual loans	29,848	26,618
Nonaccrual loans not requiring an allowance for credit losses	5	7
Recognized Interest Income	¥ 3,885	¥ 3,688

Carrying amount of loans held for sale placed on nonaccrual status.

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- Definition

Amount of interest income on financing receivable on nonaccrual status.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919258-210447

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- Definition

Amortized cost of financing receivable on nonaccrual status with no allowance for credit loss. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919258-210447

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+ References

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Amortized cost of financing receivable on nonaccrual status. Excludes net investment in lease.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=123577603&loc=d3e5111-111524

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919258-210447

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (3)

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (2)

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