XML 86 R67.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Investments - Cost, Gross Unrealized Gains and Losses, and Estimated Fair Value of Trading Investments in Fixed Income Maturities (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Schedule of Trading Securities and Other Trading Items [Line Items] |  |
Fair Market Value | $ 1,187.8 | $ 1,649.3
Debt Securities, Trading, Amortized Cost | 1,205.0 | 1,634.9
Fixed income securities - trading |  |
Schedule of Trading Securities and Other Trading Items [Line Items] |  |
Gross Unrealized Gains | 6.3 | 21.5
Gross Unrealized Losses | (23.5) | (7.1)
Fair Market Value | 1,187.8 | 1,649.3
Debt Securities, Trading, Amortized Cost | 1,205.0 | 1,634.9
Short-term investments |  |
Schedule of Trading Securities and Other Trading Items [Line Items] |  |
Gross Unrealized Gains | 0.0 | 0.0
Gross Unrealized Losses | 0.0 | 0.0
Fair Market Value | 9.5 | 73.0
Debt Securities, Trading, Amortized Cost | 9.5 | 73.0
Equity securities |  |
Schedule of Trading Securities and Other Trading Items [Line Items] |  |
Gross Unrealized Gains |  | 83.5
Gross Unrealized Losses |  | (7.3)
Fair Market Value |  | 491.0
Debt Securities, Trading, Amortized Cost |  | 414.8
Catastrophe Bonds |  |
Schedule of Trading Securities and Other Trading Items [Line Items] |  |
Gross Unrealized Gains | 0.1 | 0.0
Gross Unrealized Losses | (1.8) | (1.1)
Fair Market Value | 36.2 | 32.4
Debt Securities, Trading, Amortized Cost | 37.9 | 33.5
Total - Trading |  |
Schedule of Trading Securities and Other Trading Items [Line Items] |  |
Gross Unrealized Gains | 6.4 | 105.0
Gross Unrealized Losses | (25.3) | (15.5)
Fair Market Value | 1,233.5 | 2,245.7
Debt Securities, Trading, Amortized Cost | 1,252.4 | 2,156.2
U.S. government |  |
Schedule of Trading Securities and Other Trading Items [Line Items] |  |
Gross Unrealized Gains | 1.6 | 0.4
Gross Unrealized Losses | (0.5) | (0.8)
Fair Market Value | 147.7 | 161.9
Debt Securities, Trading, Amortized Cost | 146.6 | 162.3
Municipal |  |
Schedule of Trading Securities and Other Trading Items [Line Items] |  |
Gross Unrealized Gains | 0.0 | 0.0
Gross Unrealized Losses | (0.1) | (0.2)
Fair Market Value | 2.7 | 32.2
Debt Securities, Trading, Amortized Cost | 2.8 | 32.4
Corporate |  |
Schedule of Trading Securities and Other Trading Items [Line Items] |  |
Gross Unrealized Gains | 2.6 | 14.0
Gross Unrealized Losses | (16.6) | (4.2)
Fair Market Value | 720.2 | 1,046.3
Debt Securities, Trading, Amortized Cost | 734.2 | 1,036.5
Non-U.S. government-backed corporate |  |
Schedule of Trading Securities and Other Trading Items [Line Items] |  |
Gross Unrealized Gains |  | 6.9
Gross Unrealized Losses |  | (0.5)
Fair Market Value |  | 202.5
Debt Securities, Trading, Amortized Cost |  | 196.1
Non-U.S government |  |
Schedule of Trading Securities and Other Trading Items [Line Items] |  |
Gross Unrealized Gains | 1.9 |
Gross Unrealized Losses | (5.2) |
Fair Market Value | 265.4 |
Debt Securities, Trading, Amortized Cost | 268.7 |
Asset-backed |  |
Schedule of Trading Securities and Other Trading Items [Line Items] |  |
Gross Unrealized Gains | 0.0 | 0.0
Gross Unrealized Losses | 0.0 | 0.0
Fair Market Value | 2.4 | 9.9
Debt Securities, Trading, Amortized Cost | 2.4 | 9.9
Agency mortgage-backed |  |
Schedule of Trading Securities and Other Trading Items [Line Items] |  |
Gross Unrealized Gains | 0.2 | 0.2
Gross Unrealized Losses | (1.1) | (1.4)
Fair Market Value | 49.4 | 195.5
Debt Securities, Trading, Amortized Cost | $ 50.3 | $ 196.7

X
- Definition Trading Securities, Accumulated Gross Unrealized Gain, before Tax + References No definition available. + Details
Name: | ahl_TradingSecuritiesAccumulatedGrossUnrealizedGainbeforeTax
Namespace Prefix: | ahl_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Trading Securities, Accumulated Gross Unrealized Loss, before Tax + References No definition available. + Details
Name: | ahl_TradingSecuritiesAccumulatedGrossUnrealizedLossbeforeTax
Namespace Prefix: | ahl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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_ScheduleOfTradingSecuritiesAndOtherTradingAssetsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.4) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
Name: | us-gaap_TradingSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost of investments in debt securities classified as trading. + References No definition available. + Details
Name: | us-gaap_TradingSecuritiesDebtAmortizedCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

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_CatastropheBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_MunicipalBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ForeignCorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |