Fair Value - Fair Value Option (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Option, Quantitative Disclosures [Line Items]
Total gains (losses)	$ 73	$ (53)	$ (187)
Mortgage loans
Fair Value, Option, Quantitative Disclosures [Line Items]
Total gains (losses)	(1)	0	0
Unpaid principal balance	40	42
Mark to fair value	1	2
Fair value	41	44
Trading securities
Fair Value, Option, Quantitative Disclosures [Line Items]
Total gains (losses)	63	(33)	(313)
Investment funds
Fair Value, Option, Quantitative Disclosures [Line Items]
Total gains (losses)	30	5	(8)
Future policy benefits
Fair Value, Option, Quantitative Disclosures [Line Items]
Total gains (losses)	$ (19)	$ (25)	$ 134

Fair Value, Option, Fair Value Carrying Amount, Assets

No definition available.

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Namespace Prefix:	ahl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair Value, Option, Unpaid Principal Balance, Assets

+ References

No definition available.

+ Details

Name:	ahl_FairValueOptionUnpaidPrincipalBalanceAssets
Namespace Prefix:	ahl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of loans and long-term receivables (other than securities categorized as trading, available-for-sale or held-to-maturity) that have contractual principal amounts and for which the fair value option has been elected.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (d)(1)
-URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14064-108612

+ Details

Name:	us-gaap_FairValueOptionAggregateDifferencesLoansAndLongTermReceivables
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

For each line item in the statement of financial position, the amounts of gains and losses from fair value changes included in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14172-108612

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Period Type:	duration

- Details

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- Details

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- Details

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Namespace Prefix:
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- Details

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