Fair Value - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Corporate and Other Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	$ 20,862	$ 22,207
States, Municipalities and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	11,557	10,783
Residential Mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	4,971	5,920
Commercial Mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	2,063	1,822
Other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	955	952
Total Asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	7,989	8,694
U.S. Treasury and Obligations of Government-sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	144	182
Foreign Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	543	613
Redeemable Preferred Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	102	125
Total Fixed Maturities Available-for-sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	41,197	42,604
Fixed Maturities, Trading [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	123	161
Fixed Maturity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	41,320	42,765
Total Equity Securities Available-for-sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	185	249
Equity Securities, Trading [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	686	649
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	871	898
Short Term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	6,725	5,795
Other Invested Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	54	59
Receivables [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	7	43
Life Settlement Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	88	100
Separate Account Business [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	181	312
Payable to Brokers [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of liabilities, measured on a recurring basis	(52)	(112)
Level 1 [Member] | Corporate and Other Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	33	6
Level 1 [Member] | U.S. Treasury and Obligations of Government-sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	116	158
Level 1 [Member] | Foreign Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	81	140
Level 1 [Member] | Redeemable Preferred Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	45	40
Level 1 [Member] | Total Fixed Maturities Available-for-sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	275	344
Level 1 [Member] | Fixed Maturity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	275	344
Level 1 [Member] | Total Equity Securities Available-for-sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	126	117
Level 1 [Member] | Equity Securities, Trading [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	678	642
Level 1 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	804	759
Level 1 [Member] | Short Term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	6,162	4,990
Level 1 [Member] | Separate Account Business [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	9	4
Level 1 [Member] | Payable to Brokers [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of liabilities, measured on a recurring basis	(40)	(95)
Level 2 [Member] | Corporate and Other Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	20,625	21,982
Level 2 [Member] | States, Municipalities and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	11,486	10,687
Level 2 [Member] | Residential Mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	4,640	5,507
Level 2 [Member] | Commercial Mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	1,912	1,693
Level 2 [Member] | Other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	509	584
Level 2 [Member] | Total Asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	7,061	7,784
Level 2 [Member] | U.S. Treasury and Obligations of Government-sponsored Enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	28	24
Level 2 [Member] | Foreign Government [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	462	473
Level 2 [Member] | Redeemable Preferred Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	57	59
Level 2 [Member] | Total Fixed Maturities Available-for-sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	39,719	41,009
Level 2 [Member] | Fixed Maturities, Trading [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	43	72
Level 2 [Member] | Fixed Maturity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	39,762	41,081
Level 2 [Member] | Total Equity Securities Available-for-sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	48	98
Level 2 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	48	98
Level 2 [Member] | Short Term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	563	799
Level 2 [Member] | Other Invested Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	54	58
Level 2 [Member] | Receivables [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	5	32
Level 2 [Member] | Separate Account Business [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	171	306
Level 2 [Member] | Payable to Brokers [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of liabilities, measured on a recurring basis	(7)	(11)
Level 3 [Member] | Corporate and Other Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	204	219
Level 3 [Member] | States, Municipalities and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	71	96
Level 3 [Member] | Residential Mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	331	413
Level 3 [Member] | Commercial Mortgage-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	151	129
Level 3 [Member] | Other asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	446	368
Level 3 [Member] | Total Asset-backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	928	910
Level 3 [Member] | Redeemable Preferred Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis		26
Level 3 [Member] | Total Fixed Maturities Available-for-sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	1,203	1,251
Level 3 [Member] | Fixed Maturities, Trading [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	80	89
Level 3 [Member] | Fixed Maturity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	1,283	1,340
Level 3 [Member] | Total Equity Securities Available-for-sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	11	34
Level 3 [Member] | Equity Securities, Trading [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	8	7
Level 3 [Member] | Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	19	41
Level 3 [Member] | Short Term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis		6
Level 3 [Member] | Other Invested Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis		1
Level 3 [Member] | Receivables [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	2	11
Level 3 [Member] | Life Settlement Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	88	100
Level 3 [Member] | Separate Account Business [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of assets, measured on a recurring basis	1	2
Level 3 [Member] | Payable to Brokers [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of liabilities, measured on a recurring basis	$ (5)	$ (6)