XML 75 R38.htm IDEA: XBRL DOCUMENT v2.4.1.9
Fair Value (Details 2) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Level 3      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance $ 194.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
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= us-gaap_FairValueInputsLevel3Member
$ 164.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
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Included in earnings 1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
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Included in other comprehensive income 1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
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(1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
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Purchases 3us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
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1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
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Sales (24)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
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(10)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
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Transfers in and (out) of Level 3 (12)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
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(2)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
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Ending balance 163.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
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159.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
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Level 3 | Net realized investment gains (losses)      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Included in earnings   1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
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Level 3 | Equity in earnings of limited partnerships      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Included in earnings 1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
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Indemnity      
Fair value transfers due to changes in available market observable inputs      
Transfers from level 1 to level 2 0erie_FairValueAssetsLevel1ToLevel2TransfersAmountDuringPeriod
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0erie_FairValueAssetsLevel1ToLevel2TransfersAmountDuringPeriod
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Transfers from level 2 to level 1 0erie_FairValueAssetsLevel2ToLevel1TransfersAmountDuringPeriod
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0erie_FairValueAssetsLevel2ToLevel1TransfersAmountDuringPeriod
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Transfers from level 2 to level 3 0erie_FairValueAssetsLevel2ToLevel3TransfersAmountDuringPeriod
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0erie_FairValueAssetsLevel2ToLevel3TransfersAmountDuringPeriod
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Transfers from level 3 to level 2 0erie_FairValueAssetsLevel3ToLevel2TransfersAmountDuringPeriod
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0erie_FairValueAssetsLevel3ToLevel2TransfersAmountDuringPeriod
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Indemnity | Level 3      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance 8.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
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20.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
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Included in earnings 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
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Included in other comprehensive income 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
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Purchases 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
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Sales (1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
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(2)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
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Transfers in and (out) of Level 3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
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0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
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Ending balance 7.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
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19.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
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Indemnity | Level 3 | Available-for-sale securities      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
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Included in earnings 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
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Included in other comprehensive income 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
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Purchases 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
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Sales 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
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Transfers in and (out) of Level 3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
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Ending balance 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
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Indemnity | Level 3 | Fixed maturities | Available-for-sale securities      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
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Included in earnings 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
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Included in other comprehensive income 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
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Sales 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
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Transfers in and (out) of Level 3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
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Ending balance 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
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Indemnity | Level 3 | Corporate debt securities | Available-for-sale securities      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
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Included in earnings 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
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/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Transfers in and (out) of Level 3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Ending balance 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
1.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Indemnity | Level 3 | Collateralized debt obligations | Available-for-sale securities      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance   1.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CollateralizedDebtObligationsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Included in earnings   0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CollateralizedDebtObligationsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Included in other comprehensive income   0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CollateralizedDebtObligationsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Purchases   0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CollateralizedDebtObligationsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Sales   (1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CollateralizedDebtObligationsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Transfers in and (out) of Level 3   0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CollateralizedDebtObligationsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Ending balance   0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CollateralizedDebtObligationsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Indemnity | Level 3 | Real estate | Limited partnerships      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance 8.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
18.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Included in earnings 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Included in other comprehensive income 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Purchases 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Sales (1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
(1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Transfers in and (out) of Level 3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Ending balance 7.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
18.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
 
Exchange      
Fair value transfers due to changes in available market observable inputs      
Transfers from level 1 to level 2 0erie_FairValueAssetsLevel1ToLevel2TransfersAmountDuringPeriod
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
3erie_FairValueAssetsLevel1ToLevel2TransfersAmountDuringPeriod
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Transfers from level 2 to level 1 22erie_FairValueAssetsLevel2ToLevel1TransfersAmountDuringPeriod
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0erie_FairValueAssetsLevel2ToLevel1TransfersAmountDuringPeriod
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Transfers from level 2 to level 3 0.1erie_FairValueAssetsLevel2ToLevel3TransfersAmountDuringPeriod
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0erie_FairValueAssetsLevel2ToLevel3TransfersAmountDuringPeriod
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Transfers from level 3 to level 2 12erie_FairValueAssetsLevel3ToLevel2TransfersAmountDuringPeriod
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
2erie_FairValueAssetsLevel3ToLevel2TransfersAmountDuringPeriod
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Exchange | Fixed maturities      
Fair value transfers due to changes in available market observable inputs      
No. of securities transferred between Level 2 and Level 3 2erie_NumberOfSecuritiesTransferredFairValueAssetsBetweenLevel2AndLevel3
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
   
No. of securities transferred between Level 3 and Level 2 2erie_NumberOfSecuritiesTransferredFairValueAssetsBetweenLevel3AndLevel2
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
1erie_NumberOfSecuritiesTransferredFairValueAssetsBetweenLevel3AndLevel2
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Exchange | Nonredeemable preferred stock      
Fair value transfers due to changes in available market observable inputs      
No. of securities transferred between Level 1 and Level 2   1erie_NumberOfSecuritiesTransferredFairValueAssetsBetweenLevel1AndLevel2
/ us-gaap_InvestmentTypeAxis
= us-gaap_NonredeemablePreferredStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
No. of securities transferred between Level 2 and Level 1 2erie_NumberOfSecuritiesTransferredFairValueAssetsBetweenLevel2AndLevel1
/ us-gaap_InvestmentTypeAxis
= us-gaap_NonredeemablePreferredStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
   
Exchange | Level 3      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance 186.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
144.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in earnings 1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
6us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in other comprehensive income 1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
(1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Purchases 3us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Sales (23)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
(8)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Transfers in and (out) of Level 3 (12)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
(2)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Ending balance 156.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
140.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Exchange | Level 3 | Available-for-sale securities      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance 100.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
31.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in earnings 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in other comprehensive income 1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
(1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Purchases 3us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Sales (2)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
(3)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Transfers in and (out) of Level 3 (12)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
(2)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Ending balance 90.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
27.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Exchange | Level 3 | Trading securities      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance 15.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
15.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in earnings 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in other comprehensive income 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Purchases 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Sales 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Transfers in and (out) of Level 3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Ending balance 15.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
15.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Exchange | Level 3 | Fixed maturities | Available-for-sale securities      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance 99.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
31.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in earnings 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in other comprehensive income 1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
(1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Purchases 3us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Sales (2)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
(3)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Transfers in and (out) of Level 3 (12)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
(2)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Ending balance 89.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
26.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_DebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Exchange | Level 3 | Corporate debt securities | Available-for-sale securities      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance 87.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
26.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in earnings 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in other comprehensive income 1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Purchases 3us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Sales (2)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Transfers in and (out) of Level 3 (9)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Ending balance 80.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
26.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Exchange | Level 3 | Collateralized debt obligations | Available-for-sale securities      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance   5.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CollateralizedDebtObligationsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in earnings   1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CollateralizedDebtObligationsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in other comprehensive income   (1)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CollateralizedDebtObligationsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Purchases   0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CollateralizedDebtObligationsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Sales   (3)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CollateralizedDebtObligationsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Transfers in and (out) of Level 3   (2)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CollateralizedDebtObligationsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Ending balance   0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CollateralizedDebtObligationsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Exchange | Level 3 | Other debt securities | Available-for-sale securities      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance 12.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_OtherDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
   
Included in earnings 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_OtherDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
   
Included in other comprehensive income 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_OtherDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
   
Purchases 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_OtherDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
   
Sales 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_OtherDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
   
Transfers in and (out) of Level 3 (3)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_OtherDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
   
Ending balance 9.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_OtherDebtSecuritiesMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
   
Exchange | Level 3 | Nonredeemable preferred stock | Available-for-sale securities      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance 1.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_NonredeemablePreferredStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_NonredeemablePreferredStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in earnings 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_AvailableforsaleSecuritiesMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_NonredeemablePreferredStockMember
/ dei_LegalEntityAxis
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0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
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Included in other comprehensive income 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
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0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
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Purchases 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
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/ us-gaap_InvestmentSecondaryCategorizationAxis
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1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
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/ us-gaap_InvestmentSecondaryCategorizationAxis
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Sales 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
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= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
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/ dei_LegalEntityAxis
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0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
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/ us-gaap_InvestmentTypeAxis
= us-gaap_NonredeemablePreferredStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Transfers in and (out) of Level 3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
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0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
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/ us-gaap_InvestmentTypeAxis
= us-gaap_NonredeemablePreferredStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Ending balance 1.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
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/ us-gaap_InvestmentTypeAxis
= us-gaap_NonredeemablePreferredStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
1.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
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/ us-gaap_InvestmentTypeAxis
= us-gaap_NonredeemablePreferredStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Exchange | Level 3 | Common stock | Trading securities      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance 15.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CommonStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
15.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CommonStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in earnings 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CommonStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CommonStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in other comprehensive income 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
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/ us-gaap_InvestmentTypeAxis
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/ dei_LegalEntityAxis
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0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
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/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CommonStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Purchases 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
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/ us-gaap_InvestmentTypeAxis
= us-gaap_CommonStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ us-gaap_InvestmentTypeAxis
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/ dei_LegalEntityAxis
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Sales 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
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= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
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/ us-gaap_InvestmentTypeAxis
= us-gaap_CommonStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
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/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CommonStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Transfers in and (out) of Level 3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
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/ us-gaap_InvestmentTypeAxis
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/ dei_LegalEntityAxis
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0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
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/ us-gaap_InvestmentTypeAxis
= us-gaap_CommonStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Ending balance 15.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
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/ us-gaap_InvestmentTypeAxis
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/ dei_LegalEntityAxis
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15.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_TradingAccountAssetsMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_CommonStockMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Exchange | Level 3 | Real estate | Limited partnerships      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance 71.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
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/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
98.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in earnings 1us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
5us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
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/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Included in other comprehensive income 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
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/ us-gaap_InvestmentTypeAxis
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0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
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/ us-gaap_InvestmentSecondaryCategorizationAxis
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/ us-gaap_InvestmentTypeAxis
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Purchases 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
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= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
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0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
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= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
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/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Sales (21)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
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(5)us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
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= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
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= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Transfers in and (out) of Level 3 0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
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0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
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/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Ending balance 51.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
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/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
98.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentSecondaryCategorizationAxis
= us-gaap_PartnershipInterestMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
 
Fair value measurements on a recurring basis | Indemnity | Real estate      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance     8.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Ending balance 7.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_InvestmentTypeAxis
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/ dei_LegalEntityAxis
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  8.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Fair value measurements on a recurring basis | Exchange | Real estate      
Roll forward of consolidated level 3 fair value measurements on a recurring basis      
Beginning balance     71.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
Ending balance $ 51.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_RealEstateFundsMember
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
  $ 71.0us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_InvestmentTypeAxis
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