v3.26.1
Fair Value (Quantitative Information about Significant Unobservable Inputs Related to Material Classes of Level 3 Assets and Liabilities) (Detail)
¥ in Millions
Mar. 31, 2026
JPY (¥)
Mar. 31, 2025
JPY (¥)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt ¥ 4,693,080 ¥ 3,764,171
Trading securities and Available-for- sale | Residential mortgage-backed securities    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities   6,000
Trading securities and Available-for- sale | Commercial mortgage-backed securities    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities   3,000
Trading securities and Available-for- sale | Corporate bonds and other debt securities    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities 405,000 373,000
Derivative Financial Instruments | Other contracts    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments (1,000) 1,000
Derivative Financial Instruments | Interest rate contracts    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments (4,000) (2,000)
Derivative Financial Instruments | Foreign exchange contracts    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments 3,000 6,000
Derivative Financial Instruments | Equity-related contracts    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments (156,000) (73,000)
Derivative Financial Instruments | Credit-related contracts    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments 1,000 (2,000)
Long-term debt    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt ¥ 569,000 ¥ 489,000
Minimum | Measurement Input, Prepayment rate | Trading securities and Available-for- sale | Residential mortgage-backed securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities   0.004
Minimum | Measurement Input, Prepayment rate | Trading securities and Available-for- sale | Corporate bonds and other debt securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [1]   0.029
Minimum | Measurement Input, Default rate | Trading securities and Available-for- sale | Corporate bonds and other debt securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [1]   0.003
Minimum | Measurement Input, Default rate | Derivative Financial Instruments | Credit-related contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 0 0
Minimum | Measurement Input, Default rate | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 0 0
Minimum | Measurement Input, Recovery rate | Trading securities and Available-for- sale | Residential mortgage-backed securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities   1
Minimum | Measurement Input, Recovery rate | Trading securities and Available-for- sale | Corporate bonds and other debt securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [1]   0.365
Minimum | Measurement Input, Discount margin | Trading securities and Available-for- sale | Residential mortgage-backed securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities   0.0030
Minimum | Measurement Input, Discount margin | Trading securities and Available-for- sale | Commercial mortgage-backed securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities   0.01733
Minimum | Measurement Input, Discount margin | Trading securities and Available-for- sale | Corporate bonds and other debt securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [1] 0.00305 0.00581
Minimum | Measurement Input, Discount margin | Trading securities and Available-for- sale | Corporate bonds and other debt securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [3] 0.00679 0.0047
Minimum | Measurement Input, IR – IR correlation | Derivative Financial Instruments | Interest rate contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 0.232 0.232
Minimum | Measurement Input, IR – IR correlation | Derivative Financial Instruments | Foreign exchange contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 0.665  
Minimum | Measurement Input, IR – IR correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 0.64 0.232
Minimum | Measurement Input, FX – IR correlation | Derivative Financial Instruments | Foreign exchange contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] (0.062) 0.138
Minimum | Measurement Input, FX – IR correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] (0.062) 0.055
Minimum | Measurement Input, Equity – IR correlation | Derivative Financial Instruments | Equity-related contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 0.25 0.25
Minimum | Measurement Input, Equity – IR correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 0.25 0.25
Minimum | Measurement Input, Equity – FX correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] (0.034) (0.054)
Minimum | Measurement Input, Equity volatility | Derivative Financial Instruments | Equity-related contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 0.123 0.127
Minimum | Measurement Input, Equity volatility | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 0.103 0.103
Minimum | Measurement Input, Equity correlation | Derivative Financial Instruments | Equity-related contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 0.802  
Minimum | Measurement Input, Equity correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 0.451 0.399
Minimum | Measurement Input, Commodity volatility | Derivative Financial Instruments | Other contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 0 0.171
Minimum | Measurement Input, Credit correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 0.264 0.228
Minimum | Measurement Input, IR volatility [Member] | Derivative Financial Instruments | Interest rate contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 0.003  
Minimum | Measurement Input, IR volatility [Member] | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 0.003  
Minimum | Measurement Input, FX volatility [Member] | Derivative Financial Instruments | Foreign exchange contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 0.09  
Minimum | Measurement Input, FX volatility [Member] | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 0.09  
Maximum | Measurement Input, Prepayment rate | Trading securities and Available-for- sale | Residential mortgage-backed securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities   0.058
Maximum | Measurement Input, Prepayment rate | Trading securities and Available-for- sale | Corporate bonds and other debt securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [1]   0.029
Maximum | Measurement Input, Default rate | Trading securities and Available-for- sale | Corporate bonds and other debt securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [1]   0.003
Maximum | Measurement Input, Default rate | Derivative Financial Instruments | Credit-related contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 0.022 0.065
Maximum | Measurement Input, Default rate | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 0.065 0.068
Maximum | Measurement Input, Recovery rate | Trading securities and Available-for- sale | Residential mortgage-backed securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities   1
Maximum | Measurement Input, Recovery rate | Trading securities and Available-for- sale | Corporate bonds and other debt securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [1]   0.365
Maximum | Measurement Input, Discount margin | Trading securities and Available-for- sale | Residential mortgage-backed securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities   0.0052
Maximum | Measurement Input, Discount margin | Trading securities and Available-for- sale | Commercial mortgage-backed securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities   0.01806
Maximum | Measurement Input, Discount margin | Trading securities and Available-for- sale | Corporate bonds and other debt securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [1] 0.00305 0.00581
Maximum | Measurement Input, Discount margin | Trading securities and Available-for- sale | Corporate bonds and other debt securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [3] 0.00863 0.0047
Maximum | Measurement Input, IR – IR correlation | Derivative Financial Instruments | Interest rate contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 1 1
Maximum | Measurement Input, IR – IR correlation | Derivative Financial Instruments | Foreign exchange contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 0.665  
Maximum | Measurement Input, IR – IR correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 0.665 1
Maximum | Measurement Input, FX – IR correlation | Derivative Financial Instruments | Foreign exchange contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 0.725 0.725
Maximum | Measurement Input, FX – IR correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 0.632 0.592
Maximum | Measurement Input, Equity – IR correlation | Derivative Financial Instruments | Equity-related contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 0.25 0.25
Maximum | Measurement Input, Equity – IR correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 0.25 0.25
Maximum | Measurement Input, Equity – FX correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 0.924 0.933
Maximum | Measurement Input, Equity volatility | Derivative Financial Instruments | Equity-related contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 4.911 1.752
Maximum | Measurement Input, Equity volatility | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 0.751 0.97
Maximum | Measurement Input, Equity correlation | Derivative Financial Instruments | Equity-related contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 1  
Maximum | Measurement Input, Equity correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 1 1
Maximum | Measurement Input, Commodity volatility | Derivative Financial Instruments | Other contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 1.65 0.277
Maximum | Measurement Input, Credit correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 1 1
Maximum | Measurement Input, IR volatility [Member] | Derivative Financial Instruments | Interest rate contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 0.014  
Maximum | Measurement Input, IR volatility [Member] | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 0.014  
Maximum | Measurement Input, FX volatility [Member] | Derivative Financial Instruments | Foreign exchange contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2] 0.115  
Maximum | Measurement Input, FX volatility [Member] | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2] 0.115  
Weighted Average | Measurement Input, Prepayment rate | Trading securities and Available-for- sale | Residential mortgage-backed securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [4]   0.036
Weighted Average | Measurement Input, Prepayment rate | Trading securities and Available-for- sale | Corporate bonds and other debt securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [1],[4]   0.029
Weighted Average | Measurement Input, Default rate | Trading securities and Available-for- sale | Corporate bonds and other debt securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [1],[4]   0.003
Weighted Average | Measurement Input, Default rate | Derivative Financial Instruments | Credit-related contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2],[4] 0.004 0.014
Weighted Average | Measurement Input, Default rate | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2],[4] 0.007 0.013
Weighted Average | Measurement Input, Recovery rate | Trading securities and Available-for- sale | Residential mortgage-backed securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [4]   1
Weighted Average | Measurement Input, Recovery rate | Trading securities and Available-for- sale | Corporate bonds and other debt securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [1],[4]   0.365
Weighted Average | Measurement Input, Discount margin | Trading securities and Available-for- sale | Residential mortgage-backed securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [4]   0.00398
Weighted Average | Measurement Input, Discount margin | Trading securities and Available-for- sale | Commercial mortgage-backed securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [4]   0.01788
Weighted Average | Measurement Input, Discount margin | Trading securities and Available-for- sale | Corporate bonds and other debt securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [1],[4] 0.00305 0.00581
Weighted Average | Measurement Input, Discount margin | Trading securities and Available-for- sale | Corporate bonds and other debt securities | Discounted cash flow Price-based    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Trading securities [3],[4] 0.00711 0.0047
Weighted Average | Measurement Input, IR – IR correlation | Derivative Financial Instruments | Interest rate contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2],[4] 0.724 0.714
Weighted Average | Measurement Input, IR – IR correlation | Derivative Financial Instruments | Foreign exchange contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2],[4] 0.665  
Weighted Average | Measurement Input, IR – IR correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2],[4] 0.653 0.714
Weighted Average | Measurement Input, FX – IR correlation | Derivative Financial Instruments | Foreign exchange contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2],[4] 0.149 0.299
Weighted Average | Measurement Input, FX – IR correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2],[4] 0.149 0.299
Weighted Average | Measurement Input, Equity – IR correlation | Derivative Financial Instruments | Equity-related contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2],[4] 0.25 0.25
Weighted Average | Measurement Input, Equity – IR correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2],[4] 0.25 0.25
Weighted Average | Measurement Input, Equity – FX correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2],[4] 0 0
Weighted Average | Measurement Input, Equity volatility | Derivative Financial Instruments | Equity-related contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2],[4] 0.524 0.51
Weighted Average | Measurement Input, Equity volatility | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2],[4] 0.358 0.297
Weighted Average | Measurement Input, Equity correlation | Derivative Financial Instruments | Equity-related contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2],[4] 0.934  
Weighted Average | Measurement Input, Equity correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2],[4] 0.873 0.873
Weighted Average | Measurement Input, Commodity volatility | Derivative Financial Instruments | Other contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2],[4] 0.407 0.181
Weighted Average | Measurement Input, Credit correlation | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2],[4] 0.592 0.575
Weighted Average | Measurement Input, IR volatility [Member] | Derivative Financial Instruments | Interest rate contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2],[4] 0.008  
Weighted Average | Measurement Input, IR volatility [Member] | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2],[4] 0.008  
Weighted Average | Measurement Input, FX volatility [Member] | Derivative Financial Instruments | Foreign exchange contracts | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Derivatives financial instruments [2],[4] 0.097  
Weighted Average | Measurement Input, FX volatility [Member] | Long-term debt | Internal valuation model    
Fair Value Measurement Inputs and Valuation Techniques [Line Items]    
Long-term debt [2],[4] 0.097  
[1] These inputs are mainly used for determining the fair values of securitization products such as CDO, CLO and ABS, other than RMBS and CMBS.
[2] Internal valuation model includes discounted cash flow models and the Black-Scholes option pricing model.
[3] This input is mainly used for determining the fair values of Japanese corporate bonds.
[4] Averages are calculated by weighting each input by the relative fair value of the respective financial instruments except for derivative related inputs where medians are used.