XML 78 R67.htm IDEA: XBRL DOCUMENT v3.10.0.1

Reserves for Losses and Loss Adjustment Expenses - Short-duration Insurance Contracts, Claims Development by Accident Year (Details) $ in Millions	Sep. 30, 2018 USD ($) Claim	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Claims Development [Line Items]
Liability for claims and claims adjustment expenses, net of reinsurance	$ 4,917.5
Insurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expense, Net	5,027.8
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	3,023.0
All outstanding liabilities for 2012 and subsequent years, net of reinsurance	2,004.8
All outstanding liabilities before 2012, net of reinsurance	101.3
Liability for claims and claims adjustment expenses, net of reinsurance	2,106.1
Reinsurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expense, Net	4,797.8
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	2,555.5
All outstanding liabilities for 2012 and subsequent years, net of reinsurance	2,242.3
All outstanding liabilities before 2012, net of reinsurance	569.1
Liability for claims and claims adjustment expenses, net of reinsurance	2,811.4
Accident Year 2012 | Insurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expense, Net	644.3	$ 637.1	$ 653.6	$ 668.7	$ 654.8	$ 625.8	$ 603.9
Incurred but Not Reported (IBNR) Claims Liability, Net	$ 27.2
Number of Reported Claims | Claim	15,726
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 530.4	523.8	502.0	452.1	377.9	307.5	117.1
Accident Year 2012 | Reinsurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expense, Net	680.4	686.8	688.3	689.6	720.0	736.3	691.8
Incurred but Not Reported (IBNR) Claims Liability, Net	$ 59.5
Number of Reported Claims | Claim	3,875
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 514.0	495.8	458.1	414.2	360.4	247.7	$ 63.0
Accident Year 2013 | Insurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expense, Net	651.7	649.4	659.2	677.9	666.7	688.3
Incurred but Not Reported (IBNR) Claims Liability, Net	$ 34.4
Number of Reported Claims | Claim	14,661
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 537.4	501.9	454.2	364.2	253.9	90.4
Accident Year 2013 | Reinsurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expense, Net	497.8	503.8	523.1	548.8	571.0	578.6
Incurred but Not Reported (IBNR) Claims Liability, Net	$ 59.0
Number of Reported Claims | Claim	3,737
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 376.4	359.1	319.4	277.8	186.4	$ 63.1
Accident Year 2014 | Insurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expense, Net	696.7	693.7	701.0	728.7	754.2
Incurred but Not Reported (IBNR) Claims Liability, Net	$ 51.9
Number of Reported Claims | Claim	18,872
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 507.8	465.1	389.2	247.1	99.4
Accident Year 2014 | Reinsurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expense, Net	480.3	485.6	512.8	528.4	549.4
Incurred but Not Reported (IBNR) Claims Liability, Net	$ 76.4
Number of Reported Claims | Claim	3,769
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 314.4	288.4	247.8	172.1	$ 56.9
Accident Year 2015 | Insurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expense, Net	864.4	852.8	903.6	913.8
Incurred but Not Reported (IBNR) Claims Liability, Net	$ 124.8
Number of Reported Claims | Claim	21,221
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 544.5	470.6	326.0	119.0
Accident Year 2015 | Reinsurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expense, Net	537.8	556.6	562.7	578.5
Incurred but Not Reported (IBNR) Claims Liability, Net	$ 103.7
Number of Reported Claims | Claim	4,006
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 317.6	271.5	170.9	$ 57.4
Accident Year 2016 | Insurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expense, Net	885.7	879.6	907.3
Incurred but Not Reported (IBNR) Claims Liability, Net	$ 264.7
Number of Reported Claims | Claim	21,224
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 448.2	345.5	117.1
Accident Year 2016 | Reinsurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expense, Net	764.3	761.3	747.8
Incurred but Not Reported (IBNR) Claims Liability, Net	$ 190.5
Number of Reported Claims | Claim	3,901
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 420.7	350.5	$ 125.5
Accident Year 2017 | Insurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expense, Net	815.6	894.2
Incurred but Not Reported (IBNR) Claims Liability, Net	$ 158.6
Number of Reported Claims | Claim	21,367
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 400.2	167.5
Accident Year 2017 | Reinsurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expense, Net	1,185.0	1,187.2
Incurred but Not Reported (IBNR) Claims Liability, Net	$ 339.2
Number of Reported Claims | Claim	4,165
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 573.4	$ 227.7
Accident Year 2018 | Insurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expense, Net	469.4
Incurred but Not Reported (IBNR) Claims Liability, Net	$ 289.8
Number of Reported Claims | Claim	12,316
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 54.5
Accident Year 2018 | Reinsurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expense, Net	652.2
Incurred but Not Reported (IBNR) Claims Liability, Net	$ 517.9
Number of Reported Claims | Claim	1,971
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 39.0

X

- Definition

Undiscounted subtotal amount, after reinsurance, of the liability for unpaid claim adjustment expense for short durations insurance contracts not separately presented in claim development information.

+ References

No definition available.

+ Details

Name:	ahl_ShortDurationInsuranceContractsLiabilityforUnpaidClaimAdjustmentExpenseNetNotSeparatelyPresentedSubtotal
Namespace Prefix:	ahl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- 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

Name:	us-gaap_ClaimsDevelopmentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount, after reinsurance, of paid claims and allocated claim adjustment expense used in claims development for short-duration insurance contracts. Excludes unallocated claim adjustment expense.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 4B
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=99384497&loc=SL65671311-158438

+ Details

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

X

- Definition

Undiscounted amount, after reinsurance, of incurred-but-not-reported (IBNR) liabilities plus expected development on reported claims, for claims and allocated claim adjustment expense for short-duration insurance contracts. Excludes unallocated claim adjustment expense.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 4E
-URI http://asc.fasb.org/extlink&oid=99384497&loc=SL65671321-158438

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 4D
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99384497&loc=SL65671317-158438

+ Details

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

X

- Definition

Undiscounted amount, after reinsurance, of incurred claims and allocated claim adjustment expense used in claims development for short-duration insurance contracts. Excludes unallocated claim adjustment expense.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 4B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99384497&loc=SL65671311-158438

+ Details

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

X

- Definition

Undiscounted amount, after reinsurance, of the liability for unpaid claims and allocated claim adjustment expense for short-duration insurance contracts. Excludes unallocated claim adjustment expense.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 4C
-URI http://asc.fasb.org/extlink&oid=99384497&loc=SL65671315-158438

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 4B
-URI http://asc.fasb.org/extlink&oid=99384497&loc=SL65671311-158438

+ Details

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

X

- Definition

Undiscounted amount, after reinsurance, of the liability for unpaid claims and allocated claim adjustment expense for short-duration insurance contracts for accident years not separately presented in claim development information. Excludes unallocated claim adjustment expense.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 4B
-URI http://asc.fasb.org/extlink&oid=99384497&loc=SL65671311-158438

+ Details

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

X

- Definition

Cumulative number of reported claims for short-duration insurance contracts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=99384497&loc=SL65671317-158438

+ Details

Name:	us-gaap_ShortdurationInsuranceContractsNumberOfReportedClaims
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ProductOrServiceAxis=ahl_AssumedPropertyandCasualtyCommercialInsuranceProductLineMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortdurationInsuranceContractsAccidentYear2012Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortdurationInsuranceContractsAccidentYear2013Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortdurationInsuranceContractsAccidentYear2014Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortdurationInsuranceContractsAccidentYear2015Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortdurationInsuranceContractsAccidentYear2016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractsAccidentYear2017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractsAccidentYear2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: