v3.2.0.727
Fair Value Measurements (Financial Instruments Measured At Fair Value On Recurring Basis) (Detail) - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2015
Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Document Period End Date Jun. 30, 2015  
Available for sale, Fair Value $ 48,701 $ 49,395
Equity securities, at fair value 498 510
Short-term investments 2,062 2,322
Other investments 3,328 3,346
Securities lending collateral 1,080 1,330
Investment derivative instruments, assets 16 18
Other derivative instruments, assets 23 2
Separate account assets 1,651 1,490
Total assets measured at fair value 57,359 58,413
Investment derivative instruments, liabilities 15 36
Other derivative instruments, liability 3 25
GLB 347 406 [1]
Total liabilities measured at fair value 365 467
Fair Value, Inputs, Level 1 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 1,741 1,680
Equity securities, at fair value 483 492
Short-term investments 1,108 1,183
Other investments 370 370
Securities lending collateral 0 0
Investment derivative instruments, assets 16 18
Other derivative instruments, assets 23 0
Separate account assets 1,567 1,400
Total assets measured at fair value 5,308 5,143
Investment derivative instruments, liabilities 15 36
Other derivative instruments, liability 0 21
GLB [1] 0 0
Total liabilities measured at fair value 15 57
Fair Value, Inputs, Level 2 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 46,682 47,491
Equity securities, at fair value 13 16
Short-term investments 954 1,139
Other investments 279 257
Securities lending collateral 1,080 1,330
Investment derivative instruments, assets 0 0
Other derivative instruments, assets 0 2
Separate account assets 84 90
Total assets measured at fair value 49,092 50,325
Investment derivative instruments, liabilities 0 0
Other derivative instruments, liability 0 0
GLB [1] 0 0
Total liabilities measured at fair value 0 0
Fair Value, Inputs, Level 3 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 278 224
Equity securities, at fair value 2 2
Short-term investments 0 0
Other investments 2,679 2,719
Securities lending collateral 0 0
Investment derivative instruments, assets 0 0
Other derivative instruments, assets 0 0
Separate account assets 0 0
Total assets measured at fair value 2,959 2,945
Investment derivative instruments, liabilities 0 0
Other derivative instruments, liability 3 4
GLB [1] 347 406
Total liabilities measured at fair value 350 410
U.S. Treasury And Agency [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 2,805 2,820
U.S. Treasury And Agency [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 1,741 1,680
U.S. Treasury And Agency [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 1,064 1,140
U.S. Treasury And Agency [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 0 0
Foreign [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 15,156 15,242
Foreign [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 0 0
Foreign [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 15,100 15,220
Foreign [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 56 22
Corporate Securities [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 16,878 17,431
Corporate Securities [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 0 0
Corporate Securities [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 16,711 17,244
Corporate Securities [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 167 187
Collateralized Mortgage Backed Securities [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 10,784 10,286
Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 0 0
Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 10,729 10,271
Collateralized Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 55 15
States, Municipalities, And Political Subdivisions [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 3,078 3,616
States, Municipalities, And Political Subdivisions [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 0 0
States, Municipalities, And Political Subdivisions [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value 3,078 3,616
States, Municipalities, And Political Subdivisions [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]    
Available for sale, Fair Value $ 0 $ 0
[1] Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. Excluded from the table above is the portion of the GLB liability classified as Future policy benefits in the consolidated balance sheets. Refer to Note 5 for additional information.