v3.26.1
Other assets - Office buildings, land, equipment and facilities and Other / Other liabilities - Schedule of Breakdown of Office buildings, land, equipment and facilities (Detail) - JPY (¥)
¥ in Millions
Mar. 31, 2026
Mar. 31, 2025
Property, Plant and Equipment [Line Items]    
Office buildings, land, equipment and facilities ¥ 543,847 ¥ 436,454
Operating lease ROU assets ¥ 138,708 ¥ 156,791
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration] Office buildings, land, equipment and facilities Office buildings, land, equipment and facilities
Land [Member]    
Property, Plant and Equipment [Line Items]    
Office buildings, land, equipment and facilities ¥ 64,327 ¥ 42,934
Office buildings [Member]    
Property, Plant and Equipment [Line Items]    
Office buildings, land, equipment and facilities 52,876 46,173
Equipment and facilities [Member]    
Property, Plant and Equipment [Line Items]    
Office buildings, land, equipment and facilities 80,000 26,793
Software [Member]    
Property, Plant and Equipment [Line Items]    
Office buildings, land, equipment and facilities 170,292 143,002
Construction in progress [Member]    
Property, Plant and Equipment [Line Items]    
Office buildings, land, equipment and facilities ¥ 37,644 ¥ 20,761