Capital and funding - Summary of Comprehensive Income Reconciliation (Details) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Analysis Of Fair Value Reserves Remeasurement Of Pensions And Currency Translation Reserve [Abstract]
1 January	€ 250	€ 110
Gains/(losses) on equity instruments	147	68
Gains/(losses) on cash flow hedges	276	62
Hedging gains/(losses) transferred to non-financial assets	(171)	10
31 December	502	250	€ 110
Remeasurement of defined benefit pension plans beginning balance	(931)	(1,146)
Remeasurement of defined benefit pension plans	1,734	215	353
Remeasurement of defined benefit pension plans ending balance	803	(931)	(1,146)
Currency retranslation gains/(losses) beginning balance	(7,674)	(5,084)
Other reserves	1,025	(2,356)
Retained profit	3	(22)
Non-controlling interest	149	(212)
Currency retranslation gains/(losses) ending balance	€ (6,497)	€ (7,674)	€ (5,084)

The amount of other comprehensive income, net of tax, related to gains (losses) on remeasurements of defined benefit plans, which comprise actuarial gains and losses; the return on plan assets, excluding amounts included in net interest on the net defined benefit liability (asset); and any change in the effect of the asset ceiling, excluding amounts included in net interest on the net defined benefit liability (asset). [Refer: Other comprehensive income; Defined benefit plans [member]; Plan assets [member]; Net defined benefit liability (asset)] [Contrast: Decrease (increase) in net defined benefit liability (asset) resulting from gain (loss) on remeasurement in other comprehensive income]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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A component of equity representing the reserve of gains and losses on financial assets measured at fair value through other comprehensive income. [Refer: Financial assets measured at fair value through other comprehensive income; Other comprehensive income]

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