Estimated Fair Value of Financial Instruments (Information about Carrying Amount of Financial Instruments Reported in Consolidated Balance Sheets and Related Market or Fair Value) (Parenthetical) (Detail) - JPY (¥) ¥ in Millions	Dec. 31, 2022	Mar. 31, 2022
Estimated fair value | Investment in securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment funds	¥ 46,085	¥ 25,999