v3.26.1
Critical Accounting Estimates and Judgments - Summary of key factors of the macroeconomic scenarios on the economic conditions (Detail)
 12 Months Ended
Mar. 31, 2028
Mar. 31, 2027
Mar. 31, 2026
Japanese GDP [member] | Upside [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   3.70% 3.50%
Japanese GDP [member] | Base [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   2.40% 2.30%
Japanese GDP [member] | Downside [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   2.00% 1.70%
Japanese GDP [member] | Severe Downside [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   (2.20%) 0.90%
Japanese GDP [member] | Scenario Forecast [member] | Upside [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 4.10% 4.90%  
Japanese GDP [member] | Scenario Forecast [member] | Base [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 3.70% 3.20%  
Japanese GDP [member] | Scenario Forecast [member] | Downside [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 2.70% (0.40%)  
Japanese GDP [member] | Scenario Forecast [member] | Severe Downside [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate (0.60%) (3.70%)  
U.S. GDP [member] | Upside [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   3.30% 2.50%
U.S. GDP [member] | Base [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   2.00% 1.30%
U.S. GDP [member] | Downside [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   0.30% 0.20%
U.S. GDP [member] | Severe Downside [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   (1.10%) (1.10%)
U.S. GDP [member] | Scenario Forecast [member] | Upside [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 2.40% 3.90%  
U.S. GDP [member] | Scenario Forecast [member] | Base [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 2.00% 2.10%  
U.S. GDP [member] | Scenario Forecast [member] | Downside [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 1.00% (1.50%)  
U.S. GDP [member] | Scenario Forecast [member] | Severe Downside [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 0.70% (3.40%)  
EMU GDP [member] | Upside [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   2.90% 1.00%
EMU GDP [member] | Base [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   0.60% 0.50%
EMU GDP [member] | Downside [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   (3.20%) (0.40%)
EMU GDP [member] | Severe Downside [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   (5.40%) (0.80%)
EMU GDP [member] | Scenario Forecast [member] | Upside [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 3.10% 2.60%  
EMU GDP [member] | Scenario Forecast [member] | Base [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 1.30% 1.20%  
EMU GDP [member] | Scenario Forecast [member] | Downside [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 0.30% 0.60%  
EMU GDP [member] | Scenario Forecast [member] | Severe Downside [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate (1.40%) (0.50%)  
Asia-Pacific GDP [member] | Upside [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   5.80% 5.10%
Asia-Pacific GDP [member] | Base [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   4.50% 3.90%
Asia-Pacific GDP [member] | Downside [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   3.30% 2.80%
Asia-Pacific GDP [member] | Severe Downside [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   1.90% 1.50%
Asia-Pacific GDP [member] | Scenario Forecast [member] | Upside [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 5.00% 6.30%  
Asia-Pacific GDP [member] | Scenario Forecast [member] | Base [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 4.60% 4.50%  
Asia-Pacific GDP [member] | Scenario Forecast [member] | Downside [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 4.20% 2.80%  
Asia-Pacific GDP [member] | Scenario Forecast [member] | Severe Downside [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 3.60% 1.00%  
Japanese short-term interest rate [member] | Upside [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   0.50% 0.50%
Japanese short-term interest rate [member] | Base [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   0.50% 0.50%
Japanese short-term interest rate [member] | Downside [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   0.50% 0.50%
Japanese short-term interest rate [member] | Severe Downside [Member] | Previously Reported [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate   0.00% 1.00%
Japanese short-term interest rate [member] | Scenario Forecast [member] | Upside [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 1.00% 0.90%  
Japanese short-term interest rate [member] | Scenario Forecast [member] | Base [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 0.70% 0.70%  
Japanese short-term interest rate [member] | Scenario Forecast [member] | Downside [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 0.20% 0.50%  
Japanese short-term interest rate [member] | Scenario Forecast [member] | Severe Downside [Member]      
Disclosure of Detailed Information of key Factors of the Macroeconomic Scenarios [Line Items]      
GDP growth rate 0.30% 0.70%