| **Reinsurance (Earned Consolidated Property Casualty Insurance Premiums On Assumed And Ceded Business) (Details) (USD $)In Millions, unless otherwise specified** | 12 Months Ended                                                                                                                                        |
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| **Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]**                                                                                 |                                                                                                                                                   |   |   |
| Direct earned premiums                                                                                                                                            | $ 4,468us-gaap_DirectPremiumsEarned                                                                                                                    | $ 4,151us-gaap_DirectPremiumsEarned | $ 3,755us-gaap_DirectPremiumsEarned |
| Assumed earned premiums                                                                                                                                           | 12us-gaap_AssumedPremiumsEarned                                                                                                                        | 11us-gaap_AssumedPremiumsEarned | 9us-gaap_AssumedPremiumsEarned |
| Ceded earned premiums                                                                                                                                             | (237)us-gaap_CededPremiumsEarned                                                                                                                       | (260)us-gaap_CededPremiumsEarned | (242)us-gaap_CededPremiumsEarned |
| Property, Liability and Casualty Insurance Product Line [Member]                                                                                                  |                                                                                                                                                   |   |   |
| **Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]**                                                                                 |                                                                                                                                                   |   |   |
| Direct earned premiums                                                                                                                                            | 4,209us-gaap_DirectPremiumsEarned/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember                   | 3,903us-gaap_DirectPremiumsEarned/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember | 3,520us-gaap_DirectPremiumsEarned/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember |
| Assumed earned premiums                                                                                                                                           | 12us-gaap_AssumedPremiumsEarned/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember                     | 11us-gaap_AssumedPremiumsEarned/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember | 9us-gaap_AssumedPremiumsEarned/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember |
| Ceded earned premiums                                                                                                                                             | (176)us-gaap_CededPremiumsEarned/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember                    | (201)us-gaap_CededPremiumsEarned/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember | (185)us-gaap_CededPremiumsEarned/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember |
| Net earned premiums                                                                                                                                               | $ 4,045us-gaap_PremiumsEarnedNetPropertyAndCasualty/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember | $ 3,713us-gaap_PremiumsEarnedNetPropertyAndCasualty/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember | $ 3,344us-gaap_PremiumsEarnedNetPropertyAndCasualty/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember |

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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of earned premiums assumed from other entities.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 17 -Article 12Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 2 -Subparagraph (SX 210.12-17) -URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574992-122915Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.1) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c)(2) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 1 -Article 7
+ Details**Name:**us-gaap_AssumedPremiumsEarned**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of earned premiums ceded to other entities.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 17 -Article 12Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 2 -Subparagraph (SX 210.12-17) -URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574992-122915Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.1) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c)(2) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 1 -Article 7Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6486662&loc=d3e27175-158546
+ Details**Name:**us-gaap_CededPremiumsEarned**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount, before premiums ceded to other entities and premiums assumed by the entity, of premiums earned.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 17 -Article 12Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 2 -Subparagraph (SX 210.12-17) -URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574992-122915Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.1) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 1 -Article 7Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c)(1) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547
+ Details**Name:**us-gaap_DirectPremiumsEarned**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount, after premiums ceded to other entities and premiums assumed by the entity, of property and casualty premiums earned.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.1) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 1 -Article 7Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6486662&loc=d3e27175-158546Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547
+ Details**Name:**us-gaap_PremiumsEarnedNetPropertyAndCasualty**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
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| - Details**Name:**us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                        |
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| - Details**Name:**us-gaap_StatementBusinessSegmentsAxis=us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |