v3.26.3
Long-Duration Insurance Contracts Relating to Life Insurance Operations - Schedule of Minimum Guaranteed Interest Rates (Detail) - Fixed Annuity - JPY (¥)
¥ in Millions
Sep. 30, 2026
Mar. 31, 2026
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]    
Policy holder funds ¥ 92,384 ¥ 101,782
50-150bp    
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]    
Policy holder funds 17,837 17,947
150bp and above    
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]    
Policy holder funds 319,312 286,594
0.00% – less than 1.50%    
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]    
Policy holder funds 84,844 94,313
0.00% – less than 1.50% | 50-150bp    
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]    
Policy holder funds 17,837 17,947
0.00% – less than 1.50% | 150bp and above    
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]    
Policy holder funds 319,312 286,594
1.50% or more    
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]    
Policy holder funds 7,540 7,469
1.50% or more | 50-150bp    
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]    
Policy holder funds 0 0
1.50% or more | 150bp and above    
Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items]    
Policy holder funds ¥ 0 ¥ 0