Affiliated companies and other equity-method investees - Summary of balances and transactions with affiliated companies and other equity-method investees - Parenthetical (Details) - JPY (¥) ¥ in Millions	Mar. 31, 2020	Apr. 01, 2019
Subsidiary or Equity Method Investee [Line Items]
Operating lease right of use asset	¥ 170,782
Operating lease liability	¥ 192,160
Accounting Standards Update 2016-02 [Member]
Subsidiary or Equity Method Investee [Line Items]
Operating lease right of use asset		¥ 23,733
Operating lease liability		¥ 23,733