Transfer of Financial Assets - Additional Information (Detail) - JPY (¥) ¥ in Millions	6 Months Ended
Sep. 30, 2024	Sep. 30, 2023
Transfer of Financial Assets Accounted for as Sales [Line Items]
Installment loans	¥ 295,259	¥ 471,119
Gain (losses) on sale from securitization and loan sales	¥ 7,678	¥ 9,215

A gain (loss) realized on a transfer, accounted for as a sale, of all or a portion of financial assets in which the transferor surrenders control and receives consideration other than a beneficial interest in the assets transferred. Reflects the amount of sales proceeds in excess of, or deficient from, the sum of the carrying amounts of transferred financial assets plus transaction costs.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(9)(a))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(7)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481326/860-20-50-3

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(13))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

Name:	us-gaap_GainLossOnSecuritizationOfFinancialAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration