Invested Assets and Related Income - Summary of Fair Value of Tax Exempt Fixed Maturities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Fair value of the tax exempt fixed maturities	$ 18,421	$ 19,913
Tax Exempt Fixed Maturities [Member] | Special Revenue Bonds [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Fair value of the tax exempt fixed maturities	11,717	12,233
Tax Exempt Fixed Maturities [Member] | State General Obligation Bonds [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Fair value of the tax exempt fixed maturities	2,292	2,246
Tax Exempt Fixed Maturities [Member] | Municipal and Political Subdivision General Obligation Bonds [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Fair value of the tax exempt fixed maturities	2,220	2,505
Tax Exempt Fixed Maturities [Member] | Pre-Refunded Bonds [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Fair value of the tax exempt fixed maturities	$ 2,192	$ 2,929