Schedule I (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	$ 57,336
Fair Value	60,627
Amount at Which Shown in the Balance Sheet	60,264
Fixed maturities available for sale
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	44,666
Fair Value	47,306
Amount at Which Shown in the Balance Sheet	47,306
Fixed maturities available for sale | U.S. Treasury and agency
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	3,553
Fair Value	3,735
Amount at Which Shown in the Balance Sheet	3,735
Fixed maturities available for sale | Foreign
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	13,016
Fair Value	13,713
Amount at Which Shown in the Balance Sheet	13,713
Fixed maturities available for sale | Corporate securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	15,529
Fair Value	16,708
Amount at Which Shown in the Balance Sheet	16,708
Fixed maturities available for sale | Mortgage backed-securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	10,051
Fair Value	10,473
Amount at Which Shown in the Balance Sheet	10,473
Fixed maturities available for sale | States, municipalities, and political subdivisions
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	2,517
Fair Value	2,677
Amount at Which Shown in the Balance Sheet	2,677
Fixed maturities held to maturity
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	7,270
Fair Value	7,633
Amount at Which Shown in the Balance Sheet	7,270
Fixed maturities held to maturity | U.S. Treasury and agency
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	1,044
Fair Value	1,083
Amount at Which Shown in the Balance Sheet	1,044
Fixed maturities held to maturity | Foreign
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	910
Fair Value	964
Amount at Which Shown in the Balance Sheet	910
Fixed maturities held to maturity | Corporate securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	2,133
Fair Value	2,275
Amount at Which Shown in the Balance Sheet	2,133
Fixed maturities held to maturity | Mortgage backed-securities
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	2,028
Fair Value	2,116
Amount at Which Shown in the Balance Sheet	2,028
Fixed maturities held to maturity | States, municipalities, and political subdivisions
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	1,155
Fair Value	1,195
Amount at Which Shown in the Balance Sheet	1,155
Industrial, miscellaneous, and all others
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	707
Fair Value	744
Amount at Which Shown in the Balance Sheet	744
Short-term investments
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	2,228
Fair Value	2,228
Amount at Which Shown in the Balance Sheet	2,228
Other investments
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	2,465
Fair Value	2,716
Amount at Which Shown in the Balance Sheet	2,716
Short-term investments and Other investments, total
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	4,693
Fair Value	4,944
Amount at Which Shown in the Balance Sheet	$ 4,944