Fair Value of Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Assets
Fixed income securities	$ 44,223	$ 44,876
Equity securities	379	345
Short-term Investments	1,343	875
Other investments:
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	1,997	2,379
Municipal
Assets
Fixed income securities	4,569	4,704
Corporate
Assets
Fixed income securities	31,860	31,531
Foreign government
Assets
Fixed income securities	1,155	1,180
ABS
Assets
Fixed income securities	1,710	1,865
RMBS
Assets
Fixed income securities	1,622	1,791
CMBS
Assets
Fixed income securities	1,292	1,408
Redeemable preferred stock
Assets
Fixed income securities	18	18
Quoted prices in active markets for identical assets (Level 1)
Other investments:
Total assets at fair value	8,277	8,244
% of total assets at fair value	15.60%	15.60%
Significant other observable inputs (Level 2)
Other investments:
Total assets at fair value	42,843	42,570
% of total assets at fair value	80.90%	80.60%
Other liabilities:
Free-standing derivatives, liabilities	(155)	(91)
Total liabilities at fair value	(155)	(91)
% of total liabilities at fair value	21.50%	14.10%
Significant unobservable inputs (Level 3)
Other investments:
Total assets at fair value	1,864	2,077
% of total assets at fair value	3.50%	3.90%
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)
% of total liabilities at fair value	81.80%	90.40%
Counterparty and cash collateral netting
Other investments:
Total assets at fair value	(47)	(47)
% of total assets at fair value		(0.10%)
Other liabilities:
Free-standing derivatives, liabilities	24	29
Total liabilities at fair value	24	29
% of total liabilities at fair value	(3.30%)	(4.50%)
Fair Value
Other investments:
Total assets at fair value	52,937	52,844
% of total assets at fair value	100.00%	100.00%
Mortgage loans		4
Other investments	20	1
Limited partnership interests		1
Contract holder funds:
Derivatives embedded in life and annuity contracts	(567)	(553)
Other liabilities:
Free-standing derivatives, liabilities	(155)	(92)
Total liabilities at fair value	(722)	(645)
% of total liabilities at fair value	100.00%	100.00%
Recurring basis | Quoted prices in active markets for identical assets (Level 1)
Assets
Fixed income securities	908	1,074
Equity securities	371	338
Short-term Investments	248	220
Other investments:
Separate account assets	6,750	6,610
Other assets		2
Total assets at fair value	8,277	8,244
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | U.S. government and agencies
Assets
Fixed income securities	908	1,074
Recurring basis | Significant other observable inputs (Level 2)
Assets
Fixed income securities	41,483	41,742
Equity securities	1
Short-term Investments	1,095	655
Other investments:
Free-standing derivatives, assets	264	173
Total assets at fair value	42,843	42,570
Recurring basis | Significant other observable inputs (Level 2) | U.S. government and agencies
Assets
Fixed income securities	1,089	1,305
Recurring basis | Significant other observable inputs (Level 2) | Municipal
Assets
Fixed income securities	4,318	4,366
Recurring basis | Significant other observable inputs (Level 2) | Corporate
Assets
Fixed income securities	30,497	30,030
Recurring basis | Significant other observable inputs (Level 2) | Foreign government
Assets
Fixed income securities	1,155	1,180
Recurring basis | Significant other observable inputs (Level 2) | ABS
Assets
Fixed income securities	1,499	1,666
Recurring basis | Significant other observable inputs (Level 2) | RMBS
Assets
Fixed income securities	1,622	1,791
Recurring basis | Significant other observable inputs (Level 2) | CMBS
Assets
Fixed income securities	1,286	1,387
Recurring basis | Significant other observable inputs (Level 2) | Redeemable preferred stock
Assets
Fixed income securities	17	17
Recurring basis | Significant unobservable inputs (Level 3)
Assets
Fixed income securities	1,832	2,060
Equity securities	7	7
Other investments:
Free-standing derivatives, assets	4	3
Other assets	1	1
Total assets at fair value	1,844	2,071
Recurring basis | Significant unobservable inputs (Level 3) | Municipal
Assets
Fixed income securities	251	338
Recurring basis | Significant unobservable inputs (Level 3) | Corporate
Assets
Fixed income securities	1,363	1,501
Recurring basis | Significant unobservable inputs (Level 3) | ABS
Assets
Fixed income securities	211	199
Recurring basis | Significant unobservable inputs (Level 3) | CMBS
Assets
Fixed income securities	6	21
Recurring basis | Significant unobservable inputs (Level 3) | Redeemable preferred stock
Assets
Fixed income securities	1	1
Recurring basis | Counterparty and cash collateral netting
Other investments:
Free-standing derivatives, assets	(47)	(47)
Total assets at fair value	(47)	(47)
Recurring basis | Fair Value
Assets
Fixed income securities	44,223	44,876
Equity securities	379	345
Short-term Investments	1,343	875
Other investments:
Free-standing derivatives, assets	221	129
Separate account assets	6,750	6,610
Other assets	1	3
Total assets at fair value	52,917	52,838
Non-recurring basis | Significant unobservable inputs (Level 3)
Other investments:
Total assets at fair value	20	6
Non-recurring basis | Fair Value
Other investments:
Total assets at fair value	$ 20	$ 6