XML 76 R65.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Reserves for Losses and Loss Adjustment Expenses - Short-duration Insurance Contracts, Claims Development by Accident Year (Details) $ in Millions | Mar. 31, 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 | $ 5,021.0 |  |  |  |  |  |
Insurance |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 4,793.1 |  |  |  |  |  |
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net | 2,710.1 |  |  |  |  |  |
All outstanding liabilities for 2012 and subsequent years, net of reinsurance | 2,083.0 |  |  |  |  |  |
All outstanding liabilities before 2012, net of reinsurance | 131.1 |  |  |  |  |  |
Liability for claims and claims adjustment expenses, net of reinsurance | 2,214.1 |  |  |  |  |  |
Reinsurance |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 4,418.8 |  |  |  |  |  |
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net | 2,271.9 |  |  |  |  |  |
All outstanding liabilities for 2012 and subsequent years, net of reinsurance | 2,146.9 |  |  |  |  |  |
All outstanding liabilities before 2012, net of reinsurance | 660.0 |  |  |  |  |  |
Liability for claims and claims adjustment expenses, net of reinsurance | 2,806.9 |  |  |  |  |  |
Accident Year 2012 | Insurance |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 644.3 | $ 644.4 | $ 661.1 | $ 676.3 | $ 661.7 | $ 632.4 | $ 611.2
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 29.3 |  |  |  |  |  |
Number of Reported Claims | Claim | 15,648 |  |  |  |  |  |
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net | $ 532.0 | 530.2 | 508.0 | 457.5 | 382.2 | 310.6 | 118.5
Accident Year 2012 | Reinsurance |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 692.2 | 695.1 | 696.9 | 698.0 | 727.2 | 743.7 | 699.0
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 79.7 |  |  |  |  |  |
Number of Reported Claims | Claim | 3,791 |  |  |  |  |  |
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net | $ 508.0 | 501.5 | 463.4 | 419.2 | 364.8 | 251.4 | $ 64.0
Accident Year 2013 | Insurance |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 654.1 | 657.0 | 667.0 | 685.3 | 674.4 | 696.7 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 45.1 |  |  |  |  |  |
Number of Reported Claims | Claim | 14,597 |  |  |  |  |  |
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net | $ 524.1 | 507.9 | 459.4 | 368.5 | 257.3 | 92.1 |
Accident Year 2013 | Reinsurance |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 513.2 | 514.3 | 533.9 | 560.5 | 581.4 | 588.2 |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 72.6 |  |  |  |  |  |
Number of Reported Claims | Claim | 3,641 |  |  |  |  |  |
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net | $ 373.3 | 366.6 | 326.3 | 284.0 | 190.9 | $ 64.2 |
Accident Year 2014 | Insurance |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 705.4 | 702.6 | 709.6 | 737.6 | 763.0 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 70.8 |  |  |  |  |  |
Number of Reported Claims | Claim | 18,855 |  |  |  |  |  |
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net | $ 479.1 | 470.4 | 393.1 | 249.8 | 100.2 |  |
Accident Year 2014 | Reinsurance |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 486.4 | 495.7 | 523.1 | 539.1 | 557.6 |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 94.9 |  |  |  |  |  |
Number of Reported Claims | Claim | 3,614 |  |  |  |  |  |
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net | $ 302.1 | 293.7 | 252.3 | 175.5 | $ 57.8 |  |
Accident Year 2015 | Insurance |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 871.2 | 867.2 | 918.0 | 927.6 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 162.7 |  |  |  |  |  |
Number of Reported Claims | Claim | 21,321 |  |  |  |  |  |
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net | $ 508.4 | 478.2 | 331.4 | 120.4 |  |  |
Accident Year 2015 | Reinsurance |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 562.4 | 568.1 | 574.7 | 590.3 |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 142.0 |  |  |  |  |  |
Number of Reported Claims | Claim | 3,770 |  |  |  |  |  |
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net | $ 297.9 | 276.9 | 174.6 | $ 58.1 |  |  |
Accident Year 2016 | Insurance |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 887.7 | 892.3 | 920.4 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 300.0 |  |  |  |  |  |
Number of Reported Claims | Claim | 21,042 |  |  |  |  |  |
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net | $ 399.9 | 349.9 | 118.7 |  |  |  |
Accident Year 2016 | Reinsurance |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 775.0 | 775.5 | 761.4 |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 234.8 |  |  |  |  |  |
Number of Reported Claims | Claim | 3,492 |  |  |  |  |  |
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net | $ 372.4 | 355.5 | $ 126.9 |  |  |  |
Accident Year 2017 | Insurance |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 870.6 | 907.0 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 232.7 |  |  |  |  |  |
Number of Reported Claims | Claim | 19,494 |  |  |  |  |  |
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net | $ 261.6 | 169.4 |  |  |  |  |
Accident Year 2017 | Reinsurance |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 1,213.1 | 1,204.4 |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 483.7 |  |  |  |  |  |
Number of Reported Claims | Claim | 3,240 |  |  |  |  |  |
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net | $ 415.8 | $ 229.3 |  |  |  |  |
Accident Year 2018 | Insurance |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 159.8 |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 113.8 |  |  |  |  |  |
Number of Reported Claims | Claim | 2,636 |  |  |  |  |  |
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net | $ 5.0 |  |  |  |  |  |
Accident Year 2018 | Reinsurance |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |
Incurred Claims and Allocated Claim Adjustment Expense, Net | 176.5 |  |  |  |  |  |
Incurred but Not Reported (IBNR) Claims Liability, Net | $ 148.0 |  |  |  |  |  |
Number of Reported Claims | Claim | 1,010 |  |  |  |  |  |
Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net | $ 2.4 |  |  |  |  |  |

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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4B -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=65670685&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4D -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=65670685&loc=SL65671317-158438 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4E -URI http://asc.fasb.org/extlink&oid=65670685&loc=SL65671321-158438 + 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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4B -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=65670685&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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4B -URI http://asc.fasb.org/extlink&oid=65670685&loc=SL65671311-158438 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4C -URI http://asc.fasb.org/extlink&oid=65670685&loc=SL65671315-158438 + 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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4B -URI http://asc.fasb.org/extlink&oid=65670685&loc=SL65671311-158438 + Details
Name: | us-gaap_ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndAllocatedClaimAdjustmentExpenseNetNotSeparatelyPresented
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Number of reported claims for short-duration insurance contracts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4D -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=65670685&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: | us-gaap_ProductOrServiceAxis=us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_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=ahl_ShortDurationInsuranceContractsAccidentYear2018Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |