Invested Assets - Amortized Cost and Fair Value of Fixed Maturities and Equity Securities (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Investment Holdings [Line Items]
Tax exempt, Amortized Cost	$ 18,168	$ 17,808
Taxable, Amortized Cost	18,145	18,151
Total fixed maturities, Amortized Cost	36,313	35,959
Equity securities, Amortized Cost	1,106	1,057
Tax exempt, Gross Unrealized Appreciation	1,088	802
Taxable, Gross Unrealized Appreciation	734	655
Total fixed maturities, Gross Unrealized Appreciation	1,822	1,457
Equity securities, Gross Unrealized Appreciation	878	756
Tax exempt, Gross Unrealized Depreciation	36	189
Taxable, Gross Unrealized Depreciation	37	136
Total fixed maturities, Gross Unrealized Depreciation	73	325
Equity securities, Gross Unrealized Depreciation	15	3
Tax exempt, Fair Value	19,220	18,421
Taxable, Fair Value	18,842	18,670
Total fixed maturities, Fair Value	38,062	37,091
Equity securities, Fair Value	1,969	1,810
U.S. Government and Government Agency and Authority Obligations [Member]
Investment Holdings [Line Items]
Taxable, Amortized Cost	1,245	784
Taxable, Gross Unrealized Appreciation	43	27
Taxable, Gross Unrealized Depreciation	2	9
Taxable, Fair Value	1,286	802
Corporate Bonds [Member]
Investment Holdings [Line Items]
Taxable, Amortized Cost	8,809	9,032
Taxable, Gross Unrealized Appreciation	405	370
Taxable, Gross Unrealized Depreciation	20	88
Taxable, Fair Value	9,194	9,314
Foreign Government and Government Agency Obligations [Member]
Investment Holdings [Line Items]
Taxable, Amortized Cost	6,682	6,719
Taxable, Gross Unrealized Appreciation	236	206
Taxable, Gross Unrealized Depreciation	13	35
Taxable, Fair Value	6,905	6,890
Residential Mortgage-backed Securities [Member]
Investment Holdings [Line Items]
Taxable, Amortized Cost	229	277
Taxable, Gross Unrealized Appreciation	22	23
Taxable, Gross Unrealized Depreciation	1	1
Taxable, Fair Value	250	299
Commercial Mortgage-backed Securities [Member]
Investment Holdings [Line Items]
Taxable, Amortized Cost	1,180	1,339
Taxable, Gross Unrealized Appreciation	28	29
Taxable, Gross Unrealized Depreciation	1	3
Taxable, Fair Value	$ 1,207	$ 1,365