Invested Assets and Related Income - Amortized Cost and Fair Value of Fixed Maturities and Equity Securities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Investment Holdings [Line Items]
Tax exempt, Amortized Cost	$ 17,808	$ 18,410
Taxable, Amortized Cost	18,151	16,988
Total fixed maturities, Amortized Cost	35,959	35,398
Equity securities, Amortized Cost	1,057	1,244
Tax exempt, Gross Unrealized Appreciation	802	1,522
Taxable, Gross Unrealized Appreciation	655	1,182
Total fixed maturities, Gross Unrealized Appreciation	1,457	2,704
Equity securities, Gross Unrealized Appreciation	756	453
Tax exempt, Gross Unrealized Depreciation	189	19
Taxable, Gross Unrealized Depreciation	136	7
Total fixed maturities, Gross Unrealized Depreciation	325	26
Equity securities, Gross Unrealized Depreciation	3	34
Tax exempt, Fair Value	18,421	19,913
Taxable, Fair Value	18,670	18,163
Total fixed maturities, Fair Value	37,091	38,076
Equity securities, Fair Value	1,810	1,663
U.S. Government and Government Agency and Authority Obligations [Member]
Investment Holdings [Line Items]
Taxable, Amortized Cost	784	973
Taxable, Gross Unrealized Appreciation	27	66
Taxable, Gross Unrealized Depreciation	9
Taxable, Fair Value	802	1,039
Corporate Bonds [Member]
Investment Holdings [Line Items]
Taxable, Amortized Cost	9,032	7,331
Taxable, Gross Unrealized Appreciation	370	609
Taxable, Gross Unrealized Depreciation	88	3
Taxable, Fair Value	9,314	7,937
Foreign Government and Government Agency Obligations [Member]
Investment Holdings [Line Items]
Taxable, Amortized Cost	6,719	6,614
Taxable, Gross Unrealized Appreciation	206	395
Taxable, Gross Unrealized Depreciation	35	1
Taxable, Fair Value	6,890	7,008
Residential Mortgage-backed Securities [Member]
Investment Holdings [Line Items]
Taxable, Amortized Cost	277	421
Taxable, Gross Unrealized Appreciation	23	36
Taxable, Gross Unrealized Depreciation	1	2
Taxable, Fair Value	299	455
Commercial Mortgage-backed Securities [Member]
Investment Holdings [Line Items]
Taxable, Amortized Cost	1,339	1,649
Taxable, Gross Unrealized Appreciation	29	76
Taxable, Gross Unrealized Depreciation	3	1
Taxable, Fair Value	$ 1,365	$ 1,724