XML 68 R51.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Fair Value Measurements - Transfers between Level 1 and Level 2 (Details) $ in Millions | Dec. 31, 2017 USD ($) stock | Dec. 31, 2016 USD ($) stock | Dec. 31, 2015 USD ($) stock
--- | --- | --- | ---
Perpetual preferred stocks |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Number of stocks transferred from Level 2 to Level 1 | stock | 4 | 6 | 5
Fair value of assets transferred from Level 2 to Level 1 | $ | $ 23 | $ 35 | $ 19
Number of stocks transferred from Level 1 to Level 2 | stock | 2 | 7 | 7
Fair value of assets transferred from Level 1 to Level 2 | $ | $ 11 | $ 28 | $ 31
Common stocks |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Number of stocks transferred from Level 2 to Level 1 | stock | 0 | 3 | 7
Fair value of assets transferred from Level 2 to Level 1 | $ | $ 0 | $ 0 | $ 80
Number of stocks transferred from Level 1 to Level 2 | stock | 1 | 2 | 0
Fair value of assets transferred from Level 1 to Level 2 | $ | $ 0 | $ 0 | $ 0
Redeemable preferred stocks |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Number of stocks transferred from Level 2 to Level 1 | stock | 0 | 0 | 2
Fair value of assets transferred from Level 2 to Level 1 | $ | $ 0 | $ 0 | $ 11
Number of stocks transferred from Level 1 to Level 2 | stock | 0 | 0 | 0
Fair value of assets transferred from Level 1 to Level 2 | $ | $ 0 | $ 0 | $ 0

X
- Definition Number of stocks transferred from Level 1 to Level 2. + References No definition available. + Details
Name: | afg_NumberofStocksTransferredfromLevel1toLevel2
Namespace Prefix: | afg_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of stocks transferred from Level 2 to Level 1. + References No definition available. + Details
Name: | afg_NumberofStocksTransferredfromLevel2toLevel1
Namespace Prefix: | afg_
Data Type: | xbrli:integerItemType
Balance Type: | na
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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueAssetsLevel1ToLevel2TransfersAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueAssetsLevel2ToLevel1TransfersAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_PreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_CommonStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_RedeemablePreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |