v3.8.0.1
Investments (Fixed Maturities and Equity Securities Excluding Investments Classified as Trading) (Details) - USD ($)
$ in Millions
Dec. 31, 2017
Dec. 31, 2016
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost $ 312,385 $ 292,581
Fair Value [1] 346,780 321,419
Amortized Cost or Cost 4,147 7,149
Fair Value 6,174 9,748
Amortized Cost [1] 2,049 2,144
Fair Value 2,430 2,524
Fixed maturities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 312,385 292,581
Gross Unrealized Gains 36,171 33,463
Gross Unrealized Losses 1,776 4,625
Fair Value 346,780 321,419
Amortized Cost 2,049 2,144
Gross Unrealized Gains 381 380
Gross Unrealized Losses 0 0
Fair Value 2,430 2,524
Fixed maturities | U.S. Treasury securities and obligations of U.S. government authorities and agencies    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 22,837 21,505
Gross Unrealized Gains 3,647 3,280
Gross Unrealized Losses 346 1,001
Fair Value 26,138 23,784
Fixed maturities | Obligations of U.S. states and their political subdivisions    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 9,366 9,060
Gross Unrealized Gains 1,111 716
Gross Unrealized Losses 6 84
Fair Value 10,471 9,692
Fixed maturities | Foreign government bonds    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 88,062 79,862
Gross Unrealized Gains 15,650 16,748
Gross Unrealized Losses 293 354
Fair Value 103,419 96,256
Amortized Cost 865 839
Gross Unrealized Gains 265 262
Gross Unrealized Losses 0 0
Fair Value 1,130 1,101
Fixed maturities | U.S. corporate public securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 81,967 76,383
Gross Unrealized Gains 8,671 6,460
Gross Unrealized Losses 414 1,232
Fair Value 90,224 81,611
Fixed maturities | U.S. corporate private securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 31,852 29,974
Gross Unrealized Gains 2,051 2,122
Gross Unrealized Losses 169 308
Fair Value 33,734 31,788
Fixed maturities | Foreign corporate public securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 26,389 25,758
Gross Unrealized Gains 3,118 2,784
Gross Unrealized Losses 99 305
Fair Value 29,408 28,237
Amortized Cost 654 651
Gross Unrealized Gains 82 71
Gross Unrealized Losses 0 0
Fair Value 736 722
Fixed maturities | Foreign corporate private securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 23,322 21,383
Gross Unrealized Gains 1,242 646
Gross Unrealized Losses 337 1,149
Fair Value 24,227 20,880
Amortized Cost 84 81
Gross Unrealized Gains 2 4
Gross Unrealized Losses 0 0
Fair Value 86 85
Fixed maturities | Commercial Mortgage Backed Securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 13,134 12,589
Gross Unrealized Gains 238 240
Gross Unrealized Losses 91 125
Fair Value 13,281 12,704
Amortized Cost 0 0
Gross Unrealized Gains 0 0
Gross Unrealized Losses 0 0
Fair Value 0 0
Fixed maturities | Asset-backed securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 11,965 11,759
Gross Unrealized Gains 278 229
Gross Unrealized Losses 10 53
Fair Value 12,233 11,935
Fixed maturities | Residential mortgage-backed securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 3,491 4,308
Gross Unrealized Gains 165 238
Gross Unrealized Losses 11 14
Fair Value 3,645 4,532
Amortized Cost 446 573
Gross Unrealized Gains 32 43
Gross Unrealized Losses 0 0
Fair Value 478 616
Equity securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Gross Unrealized Gains 2,056 2,641
Gross Unrealized Losses 29 42
Amortized Cost or Cost 4,147 7,149
Fair Value 6,174 9,748
Available-for-sale | Fixed maturities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 312,385  
Fair Value 346,780  
Available-for-sale | Fixed maturities | U.S. Treasury securities and obligations of U.S. government authorities and agencies    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 22,837  
Fair Value 26,138  
Available-for-sale | Fixed maturities | Obligations of U.S. states and their political subdivisions    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 9,366  
Fair Value 10,471  
Available-for-sale | Fixed maturities | Commercial Mortgage Backed Securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 13,134  
Fair Value 13,281  
Available-for-sale | Fixed maturities | Asset-backed securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 11,965  
Fair Value 12,233  
Available-for-sale | Fixed maturities | Residential mortgage-backed securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 3,491  
Fair Value 3,645  
Available-for-sale | Equity securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 4,147  
Fair Value 6,174  
Available-for-sale | OTTI | Fixed maturities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
OTTI in AOCI (267) (337)
Available-for-sale | OTTI | Fixed maturities | U.S. Treasury securities and obligations of U.S. government authorities and agencies    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
OTTI in AOCI 0 0
Available-for-sale | OTTI | Fixed maturities | Obligations of U.S. states and their political subdivisions    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
OTTI in AOCI 0 0
Available-for-sale | OTTI | Fixed maturities | Foreign government bonds    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
OTTI in AOCI 0 0
Available-for-sale | OTTI | Fixed maturities | U.S. corporate public securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
OTTI in AOCI (10) (17)
Available-for-sale | OTTI | Fixed maturities | U.S. corporate private securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
OTTI in AOCI (13) (22)
Available-for-sale | OTTI | Fixed maturities | Foreign corporate public securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
OTTI in AOCI (5) (6)
Available-for-sale | OTTI | Fixed maturities | Foreign corporate private securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
OTTI in AOCI 0 0
Available-for-sale | OTTI | Fixed maturities | Commercial Mortgage Backed Securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
OTTI in AOCI 0 (1)
Available-for-sale | OTTI | Fixed maturities | Asset-backed securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
OTTI in AOCI (237) (288)
Available-for-sale | OTTI | Fixed maturities | Residential mortgage-backed securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
OTTI in AOCI (2) (3)
Available-for-sale | Net Unrealized Investment Gains (Losses) | Fixed maturities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
OTTI in AOCI 553 649
Held-to-maturity | Fixed maturities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost 2,049  
Fair Value 2,430  
Held-to-maturity | Fixed maturities | Commercial Mortgage Backed Securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost 0  
Fair Value 0  
Held-to-maturity | Fixed maturities | Residential mortgage-backed securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost 446  
Fair Value 478  
Held-to-maturity | Net Unrealized Investment Gains (Losses) | Fixed maturities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
OTTI in AOCI 2 1
Prudential Netting Agreement | U.S. corporate private securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Fair Value 2,660 1,456
Prudential Netting Agreement | Fixed maturities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost 4,627 4,403
Fair Value 4,913 4,403
Prudential Netting Agreement | Fixed maturities | U.S. corporate private securities    
Summary Of Investments Other Than Investments In Related Parties Reportable Data [Line Items]    
Amortized Cost or Cost 2,660 1,456
Fair Value $ 2,660 $ 1,456
[1] See Note 5 for details of balances associated with variable interest entities.