| **Transactions With Affliated Parties (Narrative) (Details) (USD $)In Millions, unless otherwise specified** | 12 Months Ended                                                                                                   |
|--------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------|
||
| **Related Party Transaction**                                                                                |                                                                                                              |   |   |
| Payment for commissions                                                                                      | $ 7us-gaap_PaymentsForCommissions                                                                                 | $ 6us-gaap_PaymentsForCommissions | $ 5us-gaap_PaymentsForCommissions |
| Earned premiums                                                                                              | 4,243us-gaap_PremiumsEarnedNet                                                                                    | 3,902us-gaap_PremiumsEarnedNet | 3,522us-gaap_PremiumsEarnedNet |
| Affiliated Parties                                                                                           |                                                                                                              |   |   |
| **Related Party Transaction**                                                                                |                                                                                                              |   |   |
| Earned premiums                                                                                              | $ 41us-gaap_PremiumsEarnedNet/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis= us-gaap_AffiliatedEntityMember | $ 35us-gaap_PremiumsEarnedNet/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis= us-gaap_AffiliatedEntityMember | $ 35us-gaap_PremiumsEarnedNet/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis= us-gaap_AffiliatedEntityMember |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of cash paid for commissions during the current period.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585
+ Details**Name:**us-gaap_PaymentsForCommissions**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 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 -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.13(c)) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882
+ Details**Name:**us-gaap_PremiumsEarnedNet**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                    |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RelatedPartyTransactionLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_AffiliatedEntityMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |