Leases - Total Amounts of Future Minimum Lease Payments Under Non-cancellable Operating Leases (Detail) - JPY (¥) ¥ in Millions	Mar. 31, 2026	Mar. 31, 2025
Disclosure of leases by lessee [line items]
Future minimum lease payments under non-cancellable operating leases	¥ 694	¥ 894
Not later than one year [member]
Disclosure of leases by lessee [line items]
Future minimum lease payments under non-cancellable operating leases	211	206
Later than one year and not later than two years [member]
Disclosure of leases by lessee [line items]
Future minimum lease payments under non-cancellable operating leases	208	208
Later than two years and not later than three years [member]
Disclosure of leases by lessee [line items]
Future minimum lease payments under non-cancellable operating leases	208	206
Later than three years and not later than four years [member]
Disclosure of leases by lessee [line items]
Future minimum lease payments under non-cancellable operating leases	¥ 67	207
Later than four years and not later than five years [member]
Disclosure of leases by lessee [line items]
Future minimum lease payments under non-cancellable operating leases		67
Later than five years [member]
Disclosure of leases by lessee [line items]
Future minimum lease payments under non-cancellable operating leases