v3.26.1
Fair Value of Financial Assets and Liabilities - Quantitative Information about Significant Unobservable Inputs Used in Fair Value Measurement for Level 3 Financial Assets and Liabilities (Detail) - JPY (¥)
¥ in Millions
12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Financial assets:    
Derivative financial instruments ¥ 10,093,100 ¥ 8,313,016
Financial liabilities:    
Derivative financial instruments 11,472,444 9,303,258
Financial liabilities designated at fair value through profit or loss 661,424 597,846
At fair value [member]    
Financial assets:    
Derivative financial instruments 10,093,100 8,313,016
Investment securities at fair value through other comprehensive income 28,774,141 33,179,136
Financial liabilities:    
Derivative financial instruments 11,472,444 9,303,258
Financial liabilities designated at fair value through profit or loss 661,424 597,846
Others (51,570) (25,320)
At fair value [member] | Currency derivatives [member]    
Financial assets:    
Derivative financial instruments 4,958,912 3,051,826
Financial liabilities:    
Derivative financial instruments 5,420,539 3,461,085
At fair value [member] | Equity derivatives [member]    
Financial assets:    
Derivative financial instruments 67,937 161,801
Financial liabilities:    
Derivative financial instruments 45,616 22,092
At fair value [member] | Credit derivatives [member]    
Financial assets:    
Derivative financial instruments 25,912 23,438
Financial liabilities:    
Derivative financial instruments 35,727 34,816
At fair value [member] | Level 3 [member]    
Financial assets:    
Derivative financial instruments 4,749 7,598
Investment securities at fair value through other comprehensive income 678,375 550,448
Financial liabilities:    
Derivative financial instruments 12,505 10,082
Financial liabilities designated at fair value through profit or loss 121,677 129,678
Others (32,464) (14,117)
At fair value [member] | Level 3 [member] | Financial liabilities at fair value through profit or loss, category [member]    
Financial liabilities:    
Financial liabilities designated at fair value through profit or loss 121,677 129,678
At fair value [member] | Level 3 [member] | Currency derivatives [member]    
Financial assets:    
Derivative financial instruments 1,423 1,059
Financial liabilities:    
Derivative financial instruments 3,142 2,950
At fair value [member] | Level 3 [member] | Equity derivatives [member]    
Financial assets:    
Derivative financial instruments 3,107 6,072
Financial liabilities:    
Derivative financial instruments 1,524 2,693
At fair value [member] | Level 3 [member] | Credit derivatives [member]    
Financial assets:    
Derivative financial instruments 205 290
Financial liabilities:    
Derivative financial instruments 127 89
At fair value [member] | Level 3 [member] | Trading assets [member] | Debt instruments [member]    
Financial assets:    
Trading assets   ¥ 41,380
At fair value [member] | Level 3 [member] | Trading assets [member] | Debt instruments [member] | Discounted cash flow [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Discount margin   9.00%
At fair value [member] | Level 3 [member] | Derivative financial assets [member] | Interest Rate Derivatives [Member]    
Financial assets:    
Derivative financial instruments 14 ¥ 177
Financial liabilities:    
Derivative financial instruments ¥ 7,712 ¥ 4,350
At fair value [member] | Level 3 [member] | Derivative financial assets [member] | Interest Rate Derivatives [Member] | Option pricing model [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Foreign exchange volatility 12.00% 11.00%
At fair value [member] | Level 3 [member] | Derivative financial assets [member] | Interest Rate Derivatives [Member] | Option pricing model [member] | Minimum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Interest rate to interest rate correlation 28.00% 29.00%
Quanto correlation 11.00% 2.00%
At fair value [member] | Level 3 [member] | Derivative financial assets [member] | Interest Rate Derivatives [Member] | Option pricing model [member] | Maximum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Interest rate to interest rate correlation 100.00% 100.00%
Quanto correlation 58.00% 52.00%
At fair value [member] | Level 3 [member] | Derivative financial assets [member] | Currency derivatives [member]    
Financial assets:    
Derivative financial instruments ¥ 1,423 ¥ 1,059
Financial liabilities:    
Derivative financial instruments ¥ 3,142 ¥ 2,950
At fair value [member] | Level 3 [member] | Derivative financial assets [member] | Currency derivatives [member] | Option pricing model [member] | Minimum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Interest rate to interest rate correlation 31.00% 30.00%
Foreign exchange volatility 10.00% 10.00%
Quanto correlation 11.00% 7.00%
At fair value [member] | Level 3 [member] | Derivative financial assets [member] | Currency derivatives [member] | Option pricing model [member] | Maximum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Interest rate to interest rate correlation 100.00% 100.00%
Foreign exchange volatility 13.00% 13.00%
Quanto correlation 50.00% 49.00%
At fair value [member] | Level 3 [member] | Derivative financial assets [member] | Equity derivatives [member] | Option pricing model [member]    
Financial assets:    
Derivative financial instruments ¥ 3,107 ¥ 6,072
Financial liabilities:    
Derivative financial instruments ¥ 1,524 ¥ 2,693
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Equity to equity correlation   59.00%
At fair value [member] | Level 3 [member] | Derivative financial assets [member] | Equity derivatives [member] | Option pricing model [member] | Minimum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Equity volatility 2.00% 2.00%
At fair value [member] | Level 3 [member] | Derivative financial assets [member] | Equity derivatives [member] | Option pricing model [member] | Maximum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Equity volatility 101.00% 93.00%
At fair value [member] | Level 3 [member] | Derivative financial assets [member] | Credit derivatives [member]    
Financial assets:    
Derivative financial instruments ¥ 205 ¥ 290
Financial liabilities:    
Derivative financial instruments ¥ 127 ¥ 89
At fair value [member] | Level 3 [member] | Derivative financial assets [member] | Credit derivatives [member] | Credit default model [member] | Minimum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Quanto correlation 18.00% 18.00%
At fair value [member] | Level 3 [member] | Derivative financial assets [member] | Credit derivatives [member] | Credit default model [member] | Maximum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Quanto correlation 28.00% 30.00%
At fair value [member] | Level 3 [member] | Financial assets at fair value through profit or loss [member] | Debt instruments [member]    
Financial assets:    
Financial assets at fair value through profit or loss ¥ 864,835 ¥ 849,122
At fair value [member] | Level 3 [member] | Financial assets at fair value through profit or loss [member] | Debt instruments [member] | Option pricing model [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Foreign exchange volatility 42.00%  
At fair value [member] | Level 3 [member] | Financial assets at fair value through profit or loss [member] | Debt instruments [member] | Option pricing model [member] | Minimum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Foreign exchange volatility   13.00%
At fair value [member] | Level 3 [member] | Financial assets at fair value through profit or loss [member] | Debt instruments [member] | Option pricing model [member] | Maximum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Foreign exchange volatility   42.00%
At fair value [member] | Level 3 [member] | Financial assets at fair value through profit or loss [member] | Debt instruments [member] | Discounted cash flow [member] | Minimum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Discount margin 5.00% 6.00%
Probability of default rate 0.00% 0.00%
Loss given default rate 25.00% 20.00%
At fair value [member] | Level 3 [member] | Financial assets at fair value through profit or loss [member] | Debt instruments [member] | Discounted cash flow [member] | Maximum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Discount margin 8.00% 8.00%
Probability of default rate 19.00% 27.00%
Loss given default rate 45.00% 100.00%
At fair value [member] | Level 3 [member] | Financial assets at fair value through profit or loss [member] | Equity instruments [member]    
Financial assets:    
Financial assets at fair value through profit or loss ¥ 82,318 ¥ 80,144
At fair value [member] | Level 3 [member] | Financial assets at fair value through profit or loss [member] | Equity instruments [member] | Discounted cash flow [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Probability of default rate 0.00%  
Loss given default rate 40.00% 40.00%
At fair value [member] | Level 3 [member] | Financial assets at fair value through profit or loss [member] | Equity instruments [member] | Discounted cash flow [member] | Minimum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Probability of default rate   0.00%
At fair value [member] | Level 3 [member] | Financial assets at fair value through profit or loss [member] | Equity instruments [member] | Discounted cash flow [member] | Maximum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Probability of default rate   1.00%
At fair value [member] | Level 3 [member] | Financial assets at fair value through profit or loss [member] | Equity instruments [member] | Market comparable companies [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Price/Book value multiple 0.8  
Liquidity discount 20.00% 20.00%
At fair value [member] | Level 3 [member] | Financial assets at fair value through profit or loss [member] | Equity instruments [member] | Market comparable companies [member] | Minimum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Price/Book value multiple   0.9
At fair value [member] | Level 3 [member] | Financial assets at fair value through profit or loss [member] | Equity instruments [member] | Market comparable companies [member] | Maximum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Price/Book value multiple   1.5
At fair value [member] | Level 3 [member] | Financial assets at fair value through other comprehensive income, category [member] | Equity instruments [member]    
Financial assets:    
Investment securities at fair value through other comprehensive income ¥ 678,375 ¥ 550,448
At fair value [member] | Level 3 [member] | Financial assets at fair value through other comprehensive income, category [member] | Equity instruments [member] | Minimum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Price/Book value multiple   0.3
At fair value [member] | Level 3 [member] | Financial assets at fair value through other comprehensive income, category [member] | Equity instruments [member] | Maximum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Price/Book value multiple   3.8
At fair value [member] | Level 3 [member] | Financial assets at fair value through other comprehensive income, category [member] | Equity instruments [member] | Market comparable companies [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Liquidity discount 20.00% 20.00%
At fair value [member] | Level 3 [member] | Financial assets at fair value through other comprehensive income, category [member] | Equity instruments [member] | Market comparable companies [member] | Minimum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Price/Book value multiple 0.4  
At fair value [member] | Level 3 [member] | Financial assets at fair value through other comprehensive income, category [member] | Equity instruments [member] | Market comparable companies [member] | Maximum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Price/Book value multiple 2.3  
At fair value [member] | Level 3 [member] | Financial liabilities designated at fair value through profit or loss [member] | Financial liabilities at fair value through profit or loss, category [member]    
Financial liabilities:    
Financial liabilities designated at fair value through profit or loss ¥ 121,677 ¥ 129,678
At fair value [member] | Level 3 [member] | Financial liabilities designated at fair value through profit or loss [member] | Option pricing model [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Interest rate to interest rate correlation 31.00%  
At fair value [member] | Level 3 [member] | Financial liabilities designated at fair value through profit or loss [member] | Option pricing model [member] | Minimum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Equity to equity correlation 46.00% 51.00%
Quanto correlation (4.00%) 3.00%
Equity volatility 28.00% 22.00%
At fair value [member] | Level 3 [member] | Financial liabilities designated at fair value through profit or loss [member] | Option pricing model [member] | Maximum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Equity to equity correlation 89.00% 70.00%
Interest rate to interest rate correlation   30.00%
Quanto correlation 50.00% 49.00%
Equity volatility 60.00% 47.00%
At fair value [member] | Level 3 [member] | Financial liabilities designated at fair value through profit or loss [member] | Credit default model [member] | Minimum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Quanto correlation 18.00% 18.00%
At fair value [member] | Level 3 [member] | Financial liabilities designated at fair value through profit or loss [member] | Credit default model [member] | Maximum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Quanto correlation 28.00% 30.00%
At fair value [member] | Level 3 [member] | Others [member]    
Financial liabilities:    
Others ¥ (32,464) ¥ (14,117)
At fair value [member] | Level 3 [member] | Others [member] | Option pricing model [member] | Minimum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Interest rate to interest rate correlation 28.00% 29.00%
Quanto correlation 11.00% 2.00%
Foreign exchange volatility 10.00% 10.00%
At fair value [member] | Level 3 [member] | Others [member] | Option pricing model [member] | Maximum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Interest rate to interest rate correlation 100.00% 100.00%
Quanto correlation 58.00% 52.00%
Foreign exchange volatility 42.00% 42.00%
At fair value [member] | Level 3 [member] | Others [member] | Credit default model [member] | Minimum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Quanto correlation 18.00% 18.00%
At fair value [member] | Level 3 [member] | Others [member] | Credit default model [member] | Maximum [member]    
Disclosure of significant unobservable inputs used in fair value measurement [Abstract]    
Quanto correlation 28.00% 30.00%