Consolidated Summary of Investments - Other Than Investments in Related Parties (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	$ 40,728
Fair Value	42,613
Amount at Which Shown in the Balance Sheet	42,613
Foreign Government and Government Agency Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	6,719
Fair Value	6,890
Amount at Which Shown in the Balance Sheet	6,890
Residential Mortgage-backed Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	277
Fair Value	299
Amount at Which Shown in the Balance Sheet	299
Commercial Mortgage-backed Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	1,339
Fair Value	1,365
Amount at Which Shown in the Balance Sheet	1,365
Short Term Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	2,114
Fair Value	2,114
Amount at Which Shown in the Balance Sheet	2,114
Fixed Maturities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	35,959
Fair Value	37,091
Amount at Which Shown in the Balance Sheet	37,091
United States Government and Government Agencies and Authorities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	401
Fair Value	414
Amount at Which Shown in the Balance Sheet	414
States, Municipalities and Political Subdivisions [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	18,191
Fair Value	18,809
Amount at Which Shown in the Balance Sheet	18,809
Public Utilities, Bonds [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	1,186
Fair Value	1,273
Amount at Which Shown in the Balance Sheet	1,273
All Other Corporate Bonds [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	7,846
Fair Value	8,041
Amount at Which Shown in the Balance Sheet	8,041
Public Utilities, Equities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	114
Fair Value	170
Amount at Which Shown in the Balance Sheet	170
Banks, Trust and Insurance, Equities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	88
Fair Value	156
Amount at Which Shown in the Balance Sheet	156
Industrial, Miscellaneous and Other [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	846
Fair Value	1,468
Amount at Which Shown in the Balance Sheet	1,468
Common Stocks [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	1,048
Fair Value	1,794
Amount at Which Shown in the Balance Sheet	1,794
Non-Redeemable Preferred Stocks [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	9
Fair Value	16
Amount at Which Shown in the Balance Sheet	16
Equity Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	1,057
Fair Value	1,810
Amount at Which Shown in the Balance Sheet	1,810
Other Invested Assets [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost or Amortized Cost	1,598
Fair Value	1,598
Amount at Which Shown in the Balance Sheet	$ 1,598