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Investments (Aggregate Fair Value And Gross Unrealized Loss By Length Of Time Security Has Continuously Been In Unrealized Loss Position) (Detail) - USD ($) $ in Millions | Jun. 30, 2015 | Dec. 31, 2014
--- | --- | ---
Investment [Line Items] |  |
Investment securities, Unrealized loss position, 0-12 Months, Fair Value | $ 16,679 | $ 8,559
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss | (394) | (244)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value | 1,512 | 3,932
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss | (62) | (79)
Investment securities, Unrealized loss position, Total Fair Value | 18,191 | 12,491
Investment securities, Unrealized loss position, Total Gross Unrealized Loss | (456) | (323)
U.S. Treasury And Agency [Member] |  |
Investment [Line Items] |  |
Investment securities, Unrealized loss position, 0-12 Months, Fair Value | 693 | 350
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss | (5) | (1)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value | 137 | 666
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss | (1) | (9)
Investment securities, Unrealized loss position, Total Fair Value | 830 | 1,016
Investment securities, Unrealized loss position, Total Gross Unrealized Loss | (6) | (10)
Foreign [Member] |  |
Investment [Line Items] |  |
Investment securities, Unrealized loss position, 0-12 Months, Fair Value | 3,867 | 2,262
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss | (104) | (75)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value | 273 | 375
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss | (12) | (15)
Investment securities, Unrealized loss position, Total Fair Value | 4,140 | 2,637
Investment securities, Unrealized loss position, Total Gross Unrealized Loss | (116) | (90)
Corporate Securities [Member] |  |
Investment [Line Items] |  |
Investment securities, Unrealized loss position, 0-12 Months, Fair Value | 6,361 | 4,684
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss | (195) | (150)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value | 520 | 738
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss | (32) | (22)
Investment securities, Unrealized loss position, Total Fair Value | 6,881 | 5,422
Investment securities, Unrealized loss position, Total Gross Unrealized Loss | (227) | (172)
Collateralized Mortgage Backed Securities [Member] |  |
Investment [Line Items] |  |
Investment securities, Unrealized loss position, 0-12 Months, Fair Value | 3,430 | 704
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss | (46) | (2)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value | 495 | 1,663
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss | (15) | (28)
Investment securities, Unrealized loss position, Total Fair Value | 3,925 | 2,367
Investment securities, Unrealized loss position, Total Gross Unrealized Loss | (61) | (30)
US States and Political Subdivisions Debt Securities [Member] |  |
Investment [Line Items] |  |
Investment securities, Unrealized loss position, 0-12 Months, Fair Value | 2,215 | 458
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss | (30) | (3)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value | 87 | 490
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss | (2) | (5)
Investment securities, Unrealized loss position, Total Fair Value | 2,302 | 948
Investment securities, Unrealized loss position, Total Gross Unrealized Loss | (32) | (8)
Fixed Maturities [Member] |  |
Investment [Line Items] |  |
Investment securities, Unrealized loss position, 0-12 Months, Fair Value | 16,566 | 8,458
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss | (380) | (231)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value | 1,512 | 3,932
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss | (62) | (79)
Investment securities, Unrealized loss position, Total Fair Value | 18,078 | 12,390
Investment securities, Unrealized loss position, Total Gross Unrealized Loss | (442) | (310)
Equity Securities [Member] |  |
Investment [Line Items] |  |
Investment securities, Unrealized loss position, 0-12 Months, Fair Value | 80 | 101
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss | (12) | (13)
Investment securities, Unrealized loss position, Over 12 Months, Fair Value | 0 | 0
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss | 0 | 0
Investment securities, Unrealized loss position, Total Fair Value | 80 | 101
Investment securities, Unrealized loss position, Total Gross Unrealized Loss | (12) | $ (13)
Other Long-term Investments [Member] |  |
Investment [Line Items] |  |
Investment securities, Unrealized loss position, 0-12 Months, Fair Value | 33 |
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss | (2) |
Investment securities, Unrealized loss position, Over 12 Months, Fair Value | 0 |
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss | 0 |
Investment securities, Unrealized loss position, Total Fair Value | 33 |
Investment securities, Unrealized loss position, Total Gross Unrealized Loss | $ (2) |

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