v3.26.1
Investment in Securities (Summary of Investment in Securities) (Parenthetical) (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2026
Mar. 31, 2025
Schedule of Investments [Line Items]    
Equity securities ¥ 39,796 ¥ 41,018
Equity securities [1] 782,413 626,910
Investment Funds Elected for Fair Value Option    
Schedule of Investments [Line Items]    
Equity securities 24,845 24,960
Variable Annuity and Variable Life Insurance Contracts    
Schedule of Investments [Line Items]    
Equity securities ¥ 137,933 ¥ 132,313
[1] The amount of assets under management of variable annuity and variable life insurance contracts included in equity securities were ¥132,313 million and ¥137,933 million as of March 31, 2025 and 2026, respectively. The amount of investment funds and others elected the fair value option included in equity securities were ¥24,960 million and ¥24,845 million as of March 31, 2025 and 2026, respectively.