Related Party Transactions - Key Mgm - Guarantees - Loans past due - Other Transactions (Detail: Text Values) - EUR (€) € in Millions	Jun. 30, 2020	Dec. 31, 2019
Loans Issued and Guarantees Granted [Abstract]
Key Management Loans and commitments	€ 9	€ 10
Key Management Deposits	17	38
Collateral held for loans outstanding	5	5
Trading assets and positive market values from derivative financial transactions with associated companies	1	1
Trading liabilities and negative market values from derivative financial transactions with associated companies	€ 0	€ 0