Corporate tax rate.

No definition available.

Name:	ahl_CorporateTaxRate
Namespace Prefix:	ahl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Deferred Tax Assets, Operating Loss Carryforwards, available to offset

+ References

No definition available.

+ Details

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

- Definition

Deferred Tax Assets Operating Loss Carryforwards, s382 Limitation, Change of Ownership

+ References

No definition available.

+ Details

Name:	ahl_DeferredTaxAssetsOperatingLossCarryforwardss382LimitationChangeofOwnership
Namespace Prefix:	ahl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Income Taxes [Line Items]

+ References

No definition available.

+ Details

Name:	ahl_IncomeTaxesLineItems
Namespace Prefix:	ahl_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Operating loss carryforwards, date of expiration

+ References

No definition available.

+ Details

Name:	ahl_Operatinglosscarryforwardsdateofexpiration
Namespace Prefix:	ahl_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

US branch profits, subject to tax

+ References

No definition available.

+ Details

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

- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible capital loss carryforwards.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32632-109319

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 25
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=117330534&loc=d3e28680-109314

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32621-109319

+ Details

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

- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible charitable contribution carryforwards.

+ References

+ Details

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

- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards that are not subject to expiration dates.

+ References

No definition available.

+ Details

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

- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards that are subject to expiration dates.

+ References

No definition available.

+ Details

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

- Definition

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

+ Details

Name:	us-gaap_DeferredTaxAssetsValuationAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h)(2))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

+ Details

Name:	us-gaap_EffectiveIncomeTaxRateContinuingOperations
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I)
-URI http://asc.fasb.org/extlink&oid=116825942&loc=d3e330036-122817

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

+ Details

Name:	us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319

+ Details

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

- Definition

Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=116821951&loc=d3e32123-109318

+ Details

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

- Details

Name:	us-gaap_IncomeTaxAuthorityNameAxis=us-gaap_InternalRevenueServiceIRSMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=ahl_AspenUKMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=ahl_USOperatingSubsidiariesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityNameAxis=us-gaap_HerMajestysRevenueAndCustomsHMRCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_OtherComprehensiveIncomeLocationAxis=us-gaap_OtherComprehensiveIncomeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityNameAxis=us-gaap_OfficeOfTheTaxCommissionerBermudaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_ValuationAllowanceOperatingLossCarryforwardsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Mar. 31, 2018
Income Taxes [Line Items]
United States corporate tax at a rate		21.00%
Less valuation allowance	$ 138,900,000	$ 149,200,000
Increase (decrease) in valuation allowance	(20,900,000)	9,200,000
US branch profits, subject to tax	0	0
Internal Revenue Service (IRS)
Income Taxes [Line Items]
Net operating loss carryforwards	501,700,000	606,800,000
Operating loss carryforwards, remaining	501,700,000
Operating loss carryforwards, subject to expiration date	444,300,000
Operating loss carryforwards, not subject to expiration	57,400,000
Capital loss carryforwards	0	500,000
Charitable contribution carryforwards	1,000,000.0	1,100,000
Less valuation allowance	113,900,000	134,800,000
Internal Revenue Service (IRS) \| Aspen U.K.
Income Taxes [Line Items]
Operating loss carryforwards, subject to s382 limitation	6,500,000
Internal Revenue Service (IRS) \| U.S. operating subsidiaries
Income Taxes [Line Items]
Operating loss carryforwards, subject to s382 limitation	$ 20,800,000
Internal Revenue Service (IRS) \| Minimum
Income Taxes [Line Items]
Operating loss carryforwards, date of expiration	2030
Internal Revenue Service (IRS) \| Maximum
Income Taxes [Line Items]
Operating loss carryforwards, date of expiration	2039
U.K.
Income Taxes [Line Items]
U. K. corporate tax rate reduced during the period			19.00%
Net operating loss carryforwards	$ 99,500,000	93,200,000
Capital loss carryforwards	3,800,000
Less valuation allowance	24,800,000	14,400,000
Increase (decrease) in valuation allowance	10,400,000	28,200,000
U.K. \| Other Comprehensive Income
Income Taxes [Line Items]
Less valuation allowance	$ 0	0
Bermuda
Income Taxes [Line Items]
Bermuda tax rate	0.00%
Valuation Allowance, Operating Loss Carryforwards
Income Taxes [Line Items]
Increase (decrease) in valuation allowance	$ (20,900,000)	9,200,000
Valuation Allowance, Operating Loss Carryforwards \| U.K.
Income Taxes [Line Items]
Less valuation allowance	$ 10,400,000	$ 28,200,000