Other assets-Other / Other liabilities - Schedule of Other assets-Other and Other liabilities (Parenthetical) (Detail) - JPY (¥) ¥ in Millions	Sep. 30, 2022	Mar. 31, 2022
Other Assets Other and Other Liabilities [Line Items]
Equity securities without a readily determinable fair value, amount	¥ 65,365	¥ 65,365

Amount of investment in equity security without readily determinable fair value.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126980263&loc=SL75117539-209714

Name:	us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant