v3.26.1
Short-Term and Long-Term Debt - Additional Information (Detail) - JPY (¥)
¥ in Millions
12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2023
Mar. 31, 2022
Mar. 31, 2021
Mar. 31, 2020
Debt Instrument [Line Items]              
Borrowings ¥ 5,965,759 ¥ 5,733,118          
Net amortization expenses of bond premiums and discounts, deferred issuance costs of bonds and medium-term notes 1,578 1,455 ¥ 1,247        
Total committed credit lines 1,034,156 795,634          
Available credit lines 753,645 598,079          
Long-term committed credit lines 639,552 502,177          
Secured by shares of subsidiaries [Member]              
Debt Instrument [Line Items]              
Secured debt 149,119            
Secured by equity method investment [Member]              
Debt Instrument [Line Items]              
Secured debt 404,097            
Secured by loans to subsidiaries [Member]              
Debt Instrument [Line Items]              
Secured debt 198,764            
Investment in securities for collateral deposits and deposits for real estate transaction [Member]              
Debt Instrument [Line Items]              
Secured debt 7,922            
Subordinated Syndicated Loan              
Debt Instrument [Line Items]              
Borrowings 44,000            
Subordinated Syndicated Loan | Loan Maturing in 5 Year              
Debt Instrument [Line Items]              
Borrowings       ¥ 34,000 ¥ 10,000    
Maturity year of loan       2083 2082    
Unsecured subordinated bonds premature redemption period       5 years 5 years    
Unsecured Subordinated Debt              
Debt Instrument [Line Items]              
Borrowings 160,000            
Unsecured subordinated bonds face value ¥ 39,000 ¥ 60,000       ¥ 21,000 ¥ 40,000
Unsecured subordinated bonds year of maturity 2061 2060       2081 2080