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Deposits (Narrative) (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2026
Mar. 31, 2025
Deposits [Line Items]    
Time deposits, including certificates of deposits ("CDs"), issued in amount of JPY10 million or more, Domestic deposits ¥ 76,858,340 ¥ 69,396,042
Minimum    
Deposits [Line Items]    
Issue amount of domestic time deposits in Japanese Yen ¥ 10