Fair Value of Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Assets
Fixed income securities	$ 75,806	$ 77,017
Equity securities	4,439	4,037
Short-term Investments	3,169	2,336
Free-standing derivatives, assets	4		2
Separate account assets	6,750	6,610
Other liabilities:
Free-standing derivatives, liabilities	(24)		(72)
U.S. government and agencies
Assets
Fixed income securities	4,257	4,713
Municipal
Assets
Fixed income securities	11,862	13,069
Corporate
Assets
Fixed income securities	49,567	48,537
Foreign government
Assets
Fixed income securities	2,365	2,517
Asset-backed securities ("ABS")
Assets
Fixed income securities	3,597	3,624
Residential mortgage-backed securities ("RMBS")
Assets
Fixed income securities	2,750	3,032
Commercial mortgage-backed securities ("CMBS")
Assets
Fixed income securities	1,381	1,498
Redeemable preferred stock
Assets
Fixed income securities	27	27
Quoted prices in active markets for identical assets (Level 1)
Assets
Total assets at fair value	13,553	13,116
Assets as a percent of assets measured at fair value	15.00%	14.60%
Significant other observable inputs (Level 2)
Assets
Total assets at fair value	74,149	74,008
Assets as a percent of assets measured at fair value	82.00%	82.10%
Other liabilities:
Free-standing derivatives, liabilities	(163)	(98)
Total liabilities at fair value	(163)	(98)
Liabilities as a percent of liabilities measured at fair value	22.50%	15.10%
Significant unobservable inputs (Level 3)
Assets
Total assets at fair value	2,757	3,081
Assets as a percent of assets measured at fair value	3.00%	3.40%
Contract holder funds:
Derivatives embedded in life and annuity contracts	(567)	(553)
Other liabilities:
Free-standing derivatives, liabilities	(24)	(30)
Total liabilities at fair value	(591)	(583)
Liabilities as a percent of liabilities measured at fair value	81.50%	90.00%
Counterparty and cash collateral netting
Assets
Total assets at fair value	(50)	(57)
Assets as a percent of assets measured at fair value		(0.10%)
Other liabilities:
Free-standing derivatives, liabilities	29	33
Total liabilities at fair value	29	33
Liabilities as a percent of liabilities measured at fair value	(4.00%)	(5.10%)
Fair Value
Assets
Total assets at fair value	90,409	90,148
Assets as a percent of assets measured at fair value	100.00%	100.00%
Mortgage loans		4
Limited partnership interests		4
Other investments	20	1
Contract holder funds:
Derivatives embedded in life and annuity contracts	(567)	(553)
Other liabilities:
Free-standing derivatives, liabilities	(158)	(95)
Total liabilities at fair value	(725)	(648)
Liabilities as a percent of liabilities measured at fair value	100.00%	100.00%
Recurring | Quoted prices in active markets for identical assets (Level 1)
Assets
Fixed income securities	2,583	2,790
Equity securities	3,408	3,008
Short-term Investments	811	703
Separate account assets	6,750	6,610
Other assets	1	5
Total assets at fair value	13,553	13,116
Recurring | Quoted prices in active markets for identical assets (Level 1) | U.S. government and agencies
Assets
Fixed income securities	2,583	2,790
Recurring | Significant other observable inputs (Level 2)
Assets
Fixed income securities	70,663	71,330
Equity securities	859	858
Short-term Investments	2,358	1,633
Free-standing derivatives, assets	269	187
Total assets at fair value	74,149	74,008
Recurring | Significant other observable inputs (Level 2) | U.S. government and agencies
Assets
Fixed income securities	1,667	1,915
Recurring | Significant other observable inputs (Level 2) | Municipal
Assets
Fixed income securities	11,202	12,104
Recurring | Significant other observable inputs (Level 2) | Corporate
Assets
Fixed income securities	47,991	46,920
Recurring | Significant other observable inputs (Level 2) | Foreign government
Assets
Fixed income securities	2,365	2,517
Recurring | Significant other observable inputs (Level 2) | Asset-backed securities ("ABS")
Assets
Fixed income securities	3,321	3,373
Recurring | Significant other observable inputs (Level 2) | Residential mortgage-backed securities ("RMBS")
Assets
Fixed income securities	2,747	3,029
Recurring | Significant other observable inputs (Level 2) | Commercial mortgage-backed securities ("CMBS")
Assets
Fixed income securities	1,344	1,446
Recurring | Significant other observable inputs (Level 2) | Redeemable preferred stock
Assets
Fixed income securities	26	26
Recurring | Significant unobservable inputs (Level 3)
Assets
Fixed income securities	2,560	2,897
Equity securities	172	171
Free-standing derivatives, assets	4	3
Other assets	1	1
Total assets at fair value	2,737	3,072
Recurring | Significant unobservable inputs (Level 3) | U.S. government and agencies
Assets
Fixed income securities	7	8
Recurring | Significant unobservable inputs (Level 3) | Municipal
Assets
Fixed income securities	660	965
Recurring | Significant unobservable inputs (Level 3) | Corporate
Assets
Fixed income securities	1,576	1,617
Recurring | Significant unobservable inputs (Level 3) | Asset-backed securities ("ABS")
Assets
Fixed income securities	276	251
Recurring | Significant unobservable inputs (Level 3) | Residential mortgage-backed securities ("RMBS")
Assets
Fixed income securities	3	3
Recurring | Significant unobservable inputs (Level 3) | Commercial mortgage-backed securities ("CMBS")
Assets
Fixed income securities	37	52
Recurring | Significant unobservable inputs (Level 3) | Redeemable preferred stock
Assets
Fixed income securities	1	1
Recurring | Counterparty and cash collateral netting
Assets
Free-standing derivatives, assets	(50)	(57)
Total assets at fair value	(50)	(57)
Recurring | Fair Value
Assets
Fixed income securities	75,806	77,017
Equity securities	4,439	4,037
Short-term Investments	3,169	2,336
Free-standing derivatives, assets	223	133
Separate account assets	6,750	6,610
Other assets	2	6
Total assets at fair value	90,389	90,139
Recurring | Fair Value | U.S. government and agencies
Assets
Fixed income securities	4,257	4,713
Recurring | Fair Value | Municipal
Assets
Fixed income securities	11,862	13,069
Recurring | Fair Value | Corporate
Assets
Fixed income securities	49,567	48,537
Recurring | Fair Value | Foreign government
Assets
Fixed income securities	2,365	2,517
Recurring | Fair Value | Asset-backed securities ("ABS")
Assets
Fixed income securities	3,597	3,624
Recurring | Fair Value | Residential mortgage-backed securities ("RMBS")
Assets
Fixed income securities	2,750	3,032
Recurring | Fair Value | Commercial mortgage-backed securities ("CMBS")
Assets
Fixed income securities	1,381	1,498
Recurring | Fair Value | Redeemable preferred stock
Assets
Fixed income securities	27	27
Non-recurring | Significant unobservable inputs (Level 3)
Assets
Total assets at fair value	20	9
Non-recurring | Fair Value
Assets
Total assets at fair value	$ 20	$ 9