XML 134 R121.htm IDEA: XBRL DOCUMENT v3.23.2
Investment in Securities (Summary of Roll-forward of Allowance for Credit Losses) (Detail) - JPY (¥)
¥ in Millions
 12 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Mar. 31, 2021
Accounts And Financing Receivable For Credit Losses [Line Items]      
Beginning ¥ 153 ¥ 120 ¥ 0
Additions to the allowance for credit losses on available-for-sale debt securities for which credit losses were not previously recorded   21 120 [1]
Additional increases (decreases) to the allowance for credit losses on AFS debt securities that had an allowance recorded in a previous period, net (21)    
Increase (Decrease) from the effects of changes in foreign exchange rates 12 12  
Ending 144 153 120
Foreign municipal bond securities      
Accounts And Financing Receivable For Credit Losses [Line Items]      
Beginning 132 120 0
Additions to the allowance for credit losses on available-for-sale debt securities for which credit losses were not previously recorded   0 120 [1]
Additional increases (decreases) to the allowance for credit losses on AFS debt securities that had an allowance recorded in a previous period, net 0    
Increase (Decrease) from the effects of changes in foreign exchange rates 12 12  
Ending 144 132 120
Japanese other asset- backed securities and debt securities      
Accounts And Financing Receivable For Credit Losses [Line Items]      
Beginning 21 0  
Additions to the allowance for credit losses on available-for-sale debt securities for which credit losses were not previously recorded   21  
Additional increases (decreases) to the allowance for credit losses on AFS debt securities that had an allowance recorded in a previous period, net (21)    
Increase (Decrease) from the effects of changes in foreign exchange rates 0 0  
Ending ¥ 0 ¥ 21 ¥ 0
[1] An increase from the effects of changes in foreign exchange rates of ¥3 million was included in additions to the allowance for credit losses on available-for-sale debt securities for fiscal 2021.