Invested Assets - Amortized Cost and Fair Value of Fixed Maturities and Equity Securities (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Investment Holdings [Line Items]
Tax exempt, Amortized Cost	$ 17,923	$ 17,808
Taxable, Amortized Cost	18,408	18,151
Total fixed maturities, Amortized Cost	36,331	35,959
Equity securities, Amortized Cost	1,111	1,057
Tax exempt, Gross Unrealized Appreciation	945	802
Taxable, Gross Unrealized Appreciation	705	655
Total fixed maturities, Gross Unrealized Appreciation	1,650	1,457
Equity securities, Gross Unrealized Appreciation	766	756
Tax exempt, Gross Unrealized Depreciation	84	189
Taxable, Gross Unrealized Depreciation	72	136
Total fixed maturities, Gross Unrealized Depreciation	156	325
Equity securities, Gross Unrealized Depreciation	14	3
Tax exempt, Fair Value	18,784	18,421
Taxable, Fair Value	19,041	18,670
Total fixed maturities, Fair Value	37,825	37,091
Equity securities, Fair Value	1,863	1,810
U.S. Government and Government Agency and Authority Obligations [Member]
Investment Holdings [Line Items]
Taxable, Amortized Cost	776	784
Taxable, Gross Unrealized Appreciation	32	27
Taxable, Gross Unrealized Depreciation	3	9
Taxable, Fair Value	805	802
Corporate Bonds [Member]
Investment Holdings [Line Items]
Taxable, Amortized Cost	9,465	9,032
Taxable, Gross Unrealized Appreciation	402	370
Taxable, Gross Unrealized Depreciation	47	88
Taxable, Fair Value	9,820	9,314
Foreign Government and Government Agency Obligations [Member]
Investment Holdings [Line Items]
Taxable, Amortized Cost	6,684	6,719
Taxable, Gross Unrealized Appreciation	220	206
Taxable, Gross Unrealized Depreciation	19	35
Taxable, Fair Value	6,885	6,890
Residential Mortgage-backed Securities [Member]
Investment Holdings [Line Items]
Taxable, Amortized Cost	251	277
Taxable, Gross Unrealized Appreciation	23	23
Taxable, Gross Unrealized Depreciation	1	1
Taxable, Fair Value	273	299
Commercial Mortgage-backed Securities [Member]
Investment Holdings [Line Items]
Taxable, Amortized Cost	1,232	1,339
Taxable, Gross Unrealized Appreciation	28	29
Taxable, Gross Unrealized Depreciation	2	3
Taxable, Fair Value	$ 1,258	$ 1,365