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	Mar. 31, 2020	Mar. 31, 2019
Estimated fair value | Investment in securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investment funds	¥ 11,631	¥ 12,100