Revenue and Expenses - Revenues (Details) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Analysis of income and expense [abstract]
Revenues from rendering of services	€ 34,832	€ 34,479	€ 33,697
Lease revenues	71	76	127
Sale of goods	5,749	5,438	5,453
Total	40,652	€ 39,993	€ 39,277
Insurance revenue	€ 212

The income arising in the course of an entity's ordinary activities. Income is increases in assets, or decreases in liabilities, that result in increases in equity, other than those relating to contributions from holders of equity claims.

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