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Life Insurance Operations - Life Insurance Premiums and Related Investment Income (Parenthetical) (Detail) - JPY (¥)
¥ in Millions
12 Months Ended
Mar. 31, 2023
Mar. 31, 2022
Mar. 31, 2021
Net Investment Income [Line Items]      
Trading Securities, Unrealized Holding Gain (Loss) ¥ 18,065 ¥ 26,075 ¥ 83,643
Life insurance related investment income      
Net Investment Income [Line Items]      
Trading Securities, Unrealized Holding Gain (Loss) ¥ 851 ¥ 8,004 ¥ 61,351