XML 87 R69.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Investments - Additional Information (Narrative) (Details) $ in Millions |  |  | 1 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | ---
Dec. 18, 2017 USD ($) | Jul. 26, 2016 USD ($) | Jan. 31, 2015 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) municipal_security | Dec. 31, 2015 USD ($) | Jan. 01, 2017 USD ($) | Oct. 02, 2012
Gain (Loss) on Investments [Line Items] |  |  |  |  |  |  |  |
Held capital requirement, percentage |  |  |  | 20.00% | 100.00% |  |  |
Catastrophe bonds, trading, cost |  |  |  | $ 32.4 | $ 42.5 |  |  |
Investment in the period |  |  |  | 64.9 | 3.3 |  |  |
Proceeds from sale of equity method investments |  |  |  | (9.3) | 0.0 | $ 0.0 |  |
Equity method investment, aggregate cost |  |  |  | 66.4 | $ 12.1 | 8.9 |  |
Investment funded |  |  |  | 0.0 |  |  |  |
Number of municipal holdings | municipal_security |  |  |  |  | 1 |  |  |
Municipal holdings, fair value |  |  |  |  | $ 0.1 |  |  |
Other-than-temporary impairment charge |  |  |  | $ 0.7 | $ 0.0 | 0.0 |  |
Equity securities |  |  |  |  |  |  |  |
Gain (Loss) on Investments [Line Items] |  |  |  |  |  |  |  |
Percentage of investment |  |  |  | 5.80% |  |  |  |
BBB Emerging Market Debt |  |  |  |  |  |  |  |
Gain (Loss) on Investments [Line Items] |  |  |  |  |  |  |  |
Percentage of investment |  |  |  | 4.00% |  |  |  |
Risk Asset Portfolio Cash |  |  |  |  |  |  |  |
Gain (Loss) on Investments [Line Items] |  |  |  |  |  |  |  |
Percentage of investment |  |  |  | 0.20% |  |  |  |
BBB Emerging Market Debt And Risk Portfolio Cash |  |  |  |  |  |  |  |
Gain (Loss) on Investments [Line Items] |  |  |  |  |  |  |  |
Percentage of investment |  |  |  | 10.00% | 10.80% |  |  |
Bene |  |  |  |  |  |  |  |
Gain (Loss) on Investments [Line Items] |  |  |  |  |  |  |  |
Investment in the period |  | $ 3.3 |  | $ 0.0 | $ 3.3 |  |  |
Gross realized and unrealized gains (loss) |  |  |  | (0.3) | (0.1) | 0.0 |  |
Proceeds from sale of equity method investments |  |  |  | 0.0 |  |  |  |
Equity method investment, ownership percentage |  | 20.00% |  |  |  |  |  |
Equity method investment, aggregate cost |  |  |  | 2.9 | 3.2 | 0.0 |  |
Chaspark |  |  |  |  |  |  |  |
Gain (Loss) on Investments [Line Items] |  |  |  |  |  |  |  |
Investment in the period |  |  |  | 0.0 | 0.0 |  |  |
Percentage of ownership acquired |  |  |  |  |  |  |  | 58.50%
Gross realized and unrealized gains (loss) |  |  |  | 0.9 | 0.3 | (0.6) |  |
Proceeds from sale of equity method investments |  |  |  | (9.3) |  |  |  |
Equity method investment, aggregate cost |  |  |  | 0.0 | 8.4 | 8.1 |  |
MVI |  |  |  |  |  |  |  |
Gain (Loss) on Investments [Line Items] |  |  |  |  |  |  |  |
Investment in the period |  |  | $ 0.8 | 0.1 | 0.0 |  |  |
Gross realized and unrealized gains (loss) |  |  |  | (0.1) | (0.3) | 0.0 |  |
Proceeds from sale of equity method investments |  |  |  | 0.0 |  |  |  |
Equity method investment, aggregate cost |  |  |  | 0.5 | 0.5 | 0.8 |  |
Digital Re |  |  |  |  |  |  |  |
Gain (Loss) on Investments [Line Items] |  |  |  |  |  |  |  |
Investment in the period |  |  |  | 2.3 | 0.0 |  |  |
Proceeds from sale of equity method investments |  |  |  | 0.0 |  |  |  |
Equity method investment, ownership percentage |  |  |  |  |  |  | 49.00% |
Equity method investment, aggregate cost |  |  |  | 0.5 | 0.0 | 0.0 | $ 2.3 |
Crop Re |  |  |  |  |  |  |  |
Gain (Loss) on Investments [Line Items] |  |  |  |  |  |  |  |
Investment in the period |  |  |  | 62.5 | 0.0 |  |  |
Proceeds from sale of equity method investments |  |  |  | 0.0 |  |  |  |
Equity method investment, ownership percentage | 23.20% |  |  |  |  |  |  |
Equity method investment, aggregate cost | $ 62.5 |  |  | $ 62.5 | 0.0 | $ 0.0 |  |
Equity method investment, cash payment | $ 5.9 |  |  |  |  |  |  |
Aspen Bermuda Limited [Member] |  |  |  |  |  |  |  |
Gain (Loss) on Investments [Line Items] |  |  |  |  |  |  |  |
Transfer from Investments |  |  |  |  | $ 95.1 |  |  |
CGB Insurance Diversified Services, Inc. | Crop Re |  |  |  |  |  |  |  |
Gain (Loss) on Investments [Line Items] |  |  |  |  |  |  |  |
Equity method investment, counterparty ownership percentage | 76.80% |  |  |  |  |  |  |

X
- Definition Catastrophe Bond + References No definition available. + Details
Name: | ahl_CatastropheBond
Namespace Prefix: | ahl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Equity Method Investment, Counterparty Ownership Percentage + References No definition available. + Details
Name: | ahl_EquityMethodInvestmentCounterpartyOwnershipPercentage
Namespace Prefix: | ahl_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Held capital requirement, percentage + References No definition available. + Details
Name: | ahl_Heldcapitalrequirementpercentage
Namespace Prefix: | ahl_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Investment Funds + References No definition available. + Details
Name: | ahl_InvestmentFunds
Namespace Prefix: | ahl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Investment Owned, Percentage + References No definition available. + Details
Name: | ahl_InvestmentOwnedPercentage
Namespace Prefix: | ahl_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Municipal Holdings + References No definition available. + Details
Name: | ahl_MunicipalHoldings
Namespace Prefix: | ahl_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Number of municipal holdings. + References No definition available. + Details
Name: | ahl_NumberOfMunicipalHoldings
Namespace Prefix: | ahl_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition This element represents the aggregate cost of investments accounted for under the equity method of accounting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_EquityMethodInvestmentAggregateCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571 + Details
Name: | us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 35 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=82895926&loc=d3e25351-111560 + Details
Name: | us-gaap_ImpairmentOfInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(12)) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(10)) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=66022249&loc=d3e33749-111570 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(13)(f)) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 + Details
Name: | us-gaap_IncomeLossFromEquityMethodInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The parent entity's interest in net assets of the subsidiary, expressed as a percentage. + References No definition available. + Details
Name: | us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The net cash outflow or inflow associated with the acquisition or sale of a business segment during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3179-108585 + Details
Name: | us-gaap_PaymentsForProceedsFromBusinessesAndInterestInAffiliates
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The cash outflow associated with the purchase of or advances to an equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585 + Details
Name: | us-gaap_PaymentsToAcquireEquityMethodInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The cash inflow associated with the sale of equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3179-108585 + Details
Name: | us-gaap_ProceedsFromSaleOfEquityMethodInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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_ScheduleOfGainLossOnInvestmentsIncludingMarketableSecuritiesAndInvestmentsHeldAtCostIncomeStatementReportedAmountsSummaryLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Value of investments transferred from the entity's investments in noncash transactions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4313-108586 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4332-108586 + Details
Name: | us-gaap_TransferOfInvestments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=ahl_BBBEmergingMarketDebtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=ahl_RiskAssetPortfolioCashMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=ahl_BBBEmergingMarketDebtAndRiskPortfolioCashMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=ahl_BeneAssicurazioniMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=ahl_ChasparkMaritimeHoldingsLtdMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=ahl_MVIMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=ahl_DigitalRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=ahl_CropReMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ConsolidatedEntitiesAxis=ahl_AspenBermudaLimitedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CounterpartyNameAxis=ahl_CGBInsuranceDiversifiedServicesInc.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |