Fair Value - Additional Information (Detail) - EUR (€)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Disclosure of fair value measurement of assets and liabilities [line items]
Amount of assets and liabilities transferred to Level III	€ 263,000,000	€ 151,000,000
Transferred of financial instruments from Level III to other levels of the fair value hierarchy	517,000,000	382,000,000
Available-for-sale (AFS)	€ 89,404,000,000	€ 84,675,000,000
Weighted average own credit spread used in the valuations of embedded derivatives in insurance contracts	0.00%	0.30%
Discount rates converge linearly	10 years
Uniform last liquid point for all Aegon's major currencies (EUR, USD and GBP)	30 years
United States [member]
Disclosure of fair value measurement of assets and liabilities [line items]
Ultimate forward rate	4.25%
The Netherlands [member]
Disclosure of fair value measurement of assets and liabilities [line items]
Ultimate forward rate	3.65%
Loans [member]
Disclosure of fair value measurement of assets and liabilities [line items]
Financial assets designated at fair value through profit or loss	€ 0
Credit spread [member] \| Weighted average [member] \| Corporate bonds [member]
Disclosure of fair value measurement of assets and liabilities [line items]
Interest rate	0.00%	3.40%
Tax credit investments [member]
Disclosure of fair value measurement of assets and liabilities [line items]
Discount rate used in valuation of tax credit investments	0.00%	6.80%
Net asset value [member] \| Recurring fair value measurement [member] \| Federal Home Loan Bank shares [member]
Disclosure of fair value measurement of assets and liabilities [line items]
Available-for-sale (AFS)	€ 91,000,000	€ 176,000,000

Decrease in weighted average own credit spread used in valuations of embedded derivatives in insurance contracts.

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- Definition

Disclosure of Fair Value Measurement of Assets and Liabilities [line items]

+ References

No definition available.

+ Details

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- Definition

Number of years discount rates converge.

+ References

No definition available.

+ Details

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- Definition

Number of years, uniform last liquid point for major currencies.

+ References

No definition available.

+ Details

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- Definition

Percentage of discount rate.

+ References

No definition available.

+ Details

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- Definition

Percentage of interest rate.

+ References

No definition available.

+ Details

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- Definition

Transfers from Level2 to Level3 of fair value hierarchy, assets and liabilities.

+ References

No definition available.

+ Details

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- Definition

Transfers out of Level3 financial instrument.

+ References

No definition available.

+ Details

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- Definition

Ultimate forward rate from liquid point.

+ References

No definition available.

+ Details

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- Definition

The amount of financial assets at fair value through profit or loss that were designated as such upon initial recognition or subsequently. [Refer: At fair value [member]; Financial assets at fair value through profit or loss]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2019-01-01
-Paragraph 8
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2019-en-r&anchor=para_8_a&doctype=Standard
-URIDate 2019-03-27

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- Definition

The amount of non-derivative financial assets that are designated as available for sale or are not classified as (a) loans and receivables; (b) held-to-maturity investments; or (c) financial assets at fair value through profit or loss. [Refer: Derivative financial assets; Financial assets at fair value through profit or loss; Held-to-maturity investments]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2021-01-01
-Name IFRS
-Number 7
-IssueDate 2019-01-01
-Paragraph 8
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2017-en-b&anchor=para_8_d&doctype=Standard&book=b
-URIDate 2019-03-27

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