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Investments (Amortized Cost And Fair Value Of Available-For-Sale and Held-To-Maturity Investment Portfolios) (Detail) (USD $) In Millions, unless otherwise specified | Jun. 30, 2013 | Dec. 31, 2012
--- | --- | ---
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost | $ 6,647 |  | $ 6,122 |
Gross Unrealized Gains | 120 |  | 251 |
Gross unrealized losses | (195) |  | (152) |
Total Available-For-Sale, Fair Value | 6,572 |  | 6,221 |
Other-Than-Temporary Impairments | (18) | [1] | (20) | [1]
Held To Maturity Securities [Abstract] |  |  |  |
Amortized Cost | 2,818 |  | 2,829 |
Gross Unrealized Gains | 3 |  | 2 |
Gross Unrealized Losses | (131) |  | (157) |
Total Held-To-Maturity, Fair Value | 2,690 |  | 2,674 |
Other-Than-Temporary Impairments | 0 | [1] | 0 | [1]
State And Municipal Bonds [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost |  |  | 38 |
Gross Unrealized Gains |  |  | 3 |
Gross unrealized losses |  |  | 0 |
Total Available-For-Sale, Fair Value |  |  | 41 |
Other-Than-Temporary Impairments |  |  | 0 | [1]
Corporate Obligations [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost |  |  | 177 |
Gross Unrealized Gains |  |  | 9 |
Gross unrealized losses |  |  | (6) |
Total Available-For-Sale, Fair Value |  |  | 180 |
Other-Than-Temporary Impairments |  |  | 0 | [1]
Held To Maturity Securities [Abstract] |  |  |  |
Amortized Cost | 2,818 |  | 2,829 |
Gross Unrealized Gains | 3 |  | 2 |
Gross Unrealized Losses | (131) |  | (157) |
Total Held-To-Maturity, Fair Value | 2,690 |  | 2,674 |
Other-Than-Temporary Impairments | 0 | [1] | 0 | [1]
Residential Mortgage-Backed Non-Agency [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost |  |  | 92 |
Gross Unrealized Gains |  |  | 0 |
Gross unrealized losses |  |  | (10) |
Total Available-For-Sale, Fair Value |  |  | 82 |
Other-Than-Temporary Impairments |  |  | 0 | [1]
Collateralized Debt Obligations [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost |  |  | 97 |
Gross Unrealized Gains |  |  | 0 |
Gross unrealized losses |  |  | (8) |
Total Available-For-Sale, Fair Value |  |  | 89 |
Other-Than-Temporary Impairments |  |  | 0 | [1]
Other Asset-Backed [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost |  |  | 23 |
Gross Unrealized Gains |  |  | 0 |
Gross unrealized losses |  |  | 0 |
Total Available-For-Sale, Fair Value |  |  | 23 |
Other-Than-Temporary Impairments |  |  | 0 | [1]
Money Market Securities [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost | 1,057 |  | 580 |
Gross Unrealized Gains | 0 |  | 0 |
Gross unrealized losses | 0 |  | 0 |
Total Available-For-Sale, Fair Value | 1,057 |  | 580 |
Other-Than-Temporary Impairments | 0 | [1] | 0 | [1]
Money Market Securities [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost | 321 |  | 210 |
Gross Unrealized Gains | 0 |  | 0 |
Gross unrealized losses | 0 |  | 0 |
Total Available-For-Sale, Fair Value | 321 |  | 210 |
Other-Than-Temporary Impairments | 0 | [1] | 0 | [1]
Perpetual Debt And Equity Securities [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost | 13 |  | 22 |
Gross Unrealized Gains | 1 |  | 1 |
Gross unrealized losses | 0 |  | 0 |
Total Available-For-Sale, Fair Value | 14 |  | 23 |
Other-Than-Temporary Impairments | 0 | [1] | 0 | [1]
Fixed Maturities [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost | 5,256 |  | 4,883 |
Gross Unrealized Gains | 119 |  | 238 |
Gross unrealized losses | (195) |  | (128) |
Total Available-For-Sale, Fair Value | 5,180 |  | 4,993 |
Other-Than-Temporary Impairments | (18) | [1] | (20) | [1]
Fixed Maturities [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |
Held To Maturity Securities [Abstract] |  |  |  |
Total Held-To-Maturity, Fair Value | 2,690 |  |  |
Fixed Maturities [Member] | U S Treasury And Government [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost | 1,203 |  | 819 |
Gross Unrealized Gains | 23 |  | 40 |
Gross unrealized losses | (8) |  | (1) |
Total Available-For-Sale, Fair Value | 1,218 |  | 858 |
Other-Than-Temporary Impairments | 0 | [1] | 0 | [1]
Fixed Maturities [Member] | State And Municipal Bonds [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost | 1,463 |  | 1,446 |
Gross Unrealized Gains | 35 |  | 97 |
Gross unrealized losses | (43) |  | (12) |
Total Available-For-Sale, Fair Value | 1,455 |  | 1,531 |
Other-Than-Temporary Impairments | 0 | [1] | 0 | [1]
Fixed Maturities [Member] | Foreign Governments [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost | 178 |  | 183 |
Gross Unrealized Gains | 9 |  | 13 |
Gross unrealized losses | 0 |  | 0 |
Total Available-For-Sale, Fair Value | 187 |  | 196 |
Other-Than-Temporary Impairments | 0 | [1] | 0 | [1]
Fixed Maturities [Member] | Corporate Obligations [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost | 1,055 |  | 1,058 |
Gross Unrealized Gains | 27 |  | 54 |
Gross unrealized losses | (38) |  | (20) |
Total Available-For-Sale, Fair Value | 1,044 |  | 1,092 |
Other-Than-Temporary Impairments | 0 | [1] | 5 | [1]
Fixed Maturities [Member] | Residential Mortgage-Backed Agency [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost | 892 |  | 939 |
Gross Unrealized Gains | 11 |  | 19 |
Gross unrealized losses | (21) |  | (1) |
Total Available-For-Sale, Fair Value | 882 |  | 957 |
Other-Than-Temporary Impairments | 0 | [1] | 0 | [1]
Fixed Maturities [Member] | Residential Mortgage-Backed Non-Agency [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost | 71 |  | 86 |
Gross Unrealized Gains | 11 |  | 11 |
Gross unrealized losses | (6) |  | (8) |
Total Available-For-Sale, Fair Value | 76 |  | 89 |
Other-Than-Temporary Impairments | 0 | [1] | 0 | [1]
Fixed Maturities [Member] | Commercial Mortgage-Backed [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost | 34 |  | 46 |
Gross Unrealized Gains | 0 |  | 0 |
Gross unrealized losses | (1) |  | (4) |
Total Available-For-Sale, Fair Value | 33 |  | 42 |
Other-Than-Temporary Impairments | 0 | [1] | 0 | [1]
Fixed Maturities [Member] | Collateralized Debt Obligations [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost | 215 |  | 161 |
Gross Unrealized Gains | 1 |  | 1 |
Gross unrealized losses | (66) |  | (71) |
Total Available-For-Sale, Fair Value | 150 |  | 91 |
Other-Than-Temporary Impairments | (18) | [1] | (25) | [1]
Fixed Maturities [Member] | Other Asset-Backed [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized Cost | 145 |  | 145 |
Gross Unrealized Gains | 2 |  | 3 |
Gross unrealized losses | (12) |  | (11) |
Total Available-For-Sale, Fair Value | 135 |  | 137 |
Other-Than-Temporary Impairments | $ 0 | [1] | $ 0 | [1]
[1] | Represents unrealized gains or losses on other than temporarily impaired securities recognized in AOCI, which includes the non-credit component of impairments, as well as all subsequent changes in fair value of such impaired securities reported in AOCI.

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- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=7534914&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 12 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Available-for-Sale Securities -URI http://asc.fasb.org/extlink&oid=6505594 + Details
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- Definition Carrying amount of debt securities accounted for as held-to-maturity, net of adjustments including, but not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized, and fair value hedge accounting adjustments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 20 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27232-111563 + Details
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