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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 | Sep. 30, 2013 | Dec. 31, 2012
--- | --- | ---
Available For Sale Securities [Abstract] |  |  |  |
Amortized cost | $ 6,443 |  | $ 6,122 |
Gross unrealized gains | 119 |  | 251 |
Gross unrealized losses | (185) |  | (152) |
Total available-for-sale, fair value | 6,377 |  | 6,221 |
Other-than-temporary impairments | (9) | [1] | (20) | [1]
Held To Maturity Securities [Abstract] |  |  |  |
Amortized cost | 2,809 |  | 2,829 |
Gross unrealized gains | 8 |  | 2 |
Gross unrealized losses | (251) |  | (157) |
Total held-to- maturity, fair value | 2,566 |  | 2,674 |
Other-Than-Temporary Impairments | 0 | [1] | 0 | [1]
US States And Political Subdivisions [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 | 2,809 |  | 2,829 |
Gross unrealized gains | 8 |  | 2 |
Gross unrealized losses | (251) |  | (157) |
Total held-to- maturity, fair value | 2,566 |  | 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 | 911 |  | 580 |
Gross unrealized gains | 0 |  | 0 |
Gross unrealized losses | 0 |  | 0 |
Total available-for-sale, fair value | 911 |  | 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 | 156 |  | 210 |
Gross unrealized gains | 0 |  | 0 |
Gross unrealized losses | 0 |  | 0 |
Total available-for-sale, fair value | 156 |  | 210 |
Other-than-temporary impairments | 0 | [1] | 0 | [1]
Perpetual Debt And Equity Securities [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized cost | 9 |  | 22 |
Gross unrealized gains | 1 |  | 1 |
Gross unrealized losses | 0 |  | 0 |
Total available-for-sale, fair value | 10 |  | 23 |
Other-than-temporary impairments | 0 | [1] | 0 | [1]
Fixed Maturities [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized cost | 5,367 |  | 4,883 |
Gross unrealized gains | 118 |  | 238 |
Gross unrealized losses | (185) |  | (128) |
Total available-for-sale, fair value | 5,300 |  | 4,993 |
Other-than-temporary impairments | (9) | [1] | (20) | [1]
Fixed Maturities [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |  |  |
Held To Maturity Securities [Abstract] |  |  |  |
Amortized cost | 2,809 |  |  |
Total held-to- maturity, fair value | 2,566 |  |  |
Fixed Maturities [Member] | U S Treasury And Government [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized cost | 526 |  | 819 |
Gross unrealized gains | 19 |  | 40 |
Gross unrealized losses | (8) |  | (1) |
Total available-for-sale, fair value | 537 |  | 858 |
Other-than-temporary impairments | 0 | [1] | 0 | [1]
Fixed Maturities [Member] | US States And Political Subdivisions [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized cost | 1,632 |  | 1,446 |
Gross unrealized gains | 30 |  | 97 |
Gross unrealized losses | (52) |  | (12) |
Total available-for-sale, fair value | 1,610 |  | 1,531 |
Other-than-temporary impairments | 0 | [1] | 0 | [1]
Fixed Maturities [Member] | Foreign Governments [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized cost | 192 |  | 183 |
Gross unrealized gains | 9 |  | 13 |
Gross unrealized losses | 0 |  | 0 |
Total available-for-sale, fair value | 201 |  | 196 |
Other-than-temporary impairments | 0 | [1] | 0 | [1]
Fixed Maturities [Member] | Corporate Obligations [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized cost | 1,616 |  | 1,058 |
Gross unrealized gains | 32 |  | 54 |
Gross unrealized losses | (26) |  | (20) |
Total available-for-sale, fair value | 1,622 |  | 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 | 942 |  | 939 |
Gross unrealized gains | 10 |  | 19 |
Gross unrealized losses | (18) |  | (1) |
Total available-for-sale, fair value | 934 |  | 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 | 67 |  | 86 |
Gross unrealized gains | 13 |  | 11 |
Gross unrealized losses | (6) |  | (8) |
Total available-for-sale, fair value | 74 |  | 89 |
Other-than-temporary impairments | 3 | [1] | 0 | [1]
Fixed Maturities [Member] | Commercial Mortgage-Backed [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized cost | 34 |  | 46 |
Gross unrealized gains | 1 |  | 0 |
Gross unrealized losses | (1) |  | (4) |
Total available-for-sale, fair value | 34 |  | 42 |
Other-than-temporary impairments | 0 | [1] | 0 | [1]
Fixed Maturities [Member] | Collateralized Debt Obligations [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized cost | 210 |  | 161 |
Gross unrealized gains | 2 |  | 1 |
Gross unrealized losses | (57) |  | (71) |
Total available-for-sale, fair value | 155 |  | 91 |
Other-than-temporary impairments | (12) | [1] | (25) | [1]
Fixed Maturities [Member] | Other Asset-Backed [Member] |  |  |  |
Available For Sale Securities [Abstract] |  |  |  |
Amortized cost | 148 |  | 145 |
Gross unrealized gains | 2 |  | 3 |
Gross unrealized losses | (17) |  | (11) |
Total available-for-sale, fair value | 133 |  | 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.

X
- Definition 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. + References No definition available. + Details
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- Definition Amount of accumulated pre-tax unrealized gains before deducting pre-tax unrealized losses on investments in available-for-sale securities impacting investments. + References No definition available. + Details
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- Definition Amount of accumulated pre-tax unrealized losses before deducting pre-tax unrealized gains on investments in available-for-sale securities impacting investments. + References No definition available. + Details
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- Definition 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. + References No definition available. + Details
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- Definition This item represents the excess of amortized cost over fair value of securities in a gain position and which are categorized as held-to-maturity. + References No definition available. + Details
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- Definition This item represents the excess of amortized cost over fair value of securities in a loss position and which are categorized as held-to-maturity. + References No definition available. + Details
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- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + 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=28360136&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562 + Details
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- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.1) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.6) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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