Fair Value of Assets and Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Assets
Fixed income securities	$ 24,443	$ 24,629
Equity securities	1,344	1,542
Short-term investments	1,545	816
Other investments:
Free-standing derivatives, assets			$ 2
Separate account assets	3,488	3,639
Derivative asset, fair value, gross liability and obligation to return cash, offset	$ (9)	$ (11)
% of total assets at fair value	0.00%	0.00%
Other investments	$ 4	$ 5
Other liabilities:
Free-standing derivatives, liabilities	(9)		$ (9)
Free standing derivative liabilities derivative liability, fair value, gross asset and right to reclaim cash, offset	$ 1	$ 1
% of total liabilities at fair value	(0.30%)	(0.30%)
U.S. government and agencies
Assets
Fixed income securities	$ 924	$ 977
Municipal
Assets
Fixed income securities	2,471	2,442
Foreign government
Assets
Fixed income securities	379	384
RMBS
Assets
Fixed income securities	415	451
CMBS
Assets
Fixed income securities	417	436
Redeemable preferred stock
Assets
Fixed income securities	15	15
Quoted prices in active markets for identical assets (Level 1)
Other investments:
Total assets at fair value	$ 5,432	$ 5,858
% of total assets at fair value	17.60%	19.10%
Other liabilities:
Total liabilities at fair value	$ 0	$ 0
% of total liabilities at fair value	0.00%	0.00%
Significant other observable inputs (Level 2)
Other investments:
Total assets at fair value	$ 24,698	$ 24,102
% of total assets at fair value	79.90%	78.50%
Other liabilities:
Total liabilities at fair value	$ (16)	$ (7)
% of total liabilities at fair value	4.80%	2.20%
Significant unobservable inputs (Level 3)
Other investments:
Total assets at fair value	$ 776	$ 736
% of total assets at fair value	2.50%	2.40%
Other liabilities:
Total liabilities at fair value	$ (322)	$ (307)
% of total liabilities at fair value	95.50%	98.10%
Recurring basis
Other investments:
Free Standing Derivative Assets, Derivative Asset, Fair Value, Gross Asset and Right to Reclaim Cash, Offset	$ (9)	$ (11)
Derivative asset, fair value, gross liability and obligation to return cash, offset	(9)	(11)
Other liabilities:
Free standing derivative liabilities derivative liability, fair value, gross asset and right to reclaim cash, offset	1	1
Recurring basis | Quoted prices in active markets for identical assets (Level 1)
Assets
Fixed income securities	484	546
Equity securities	1,285	1,479
Short-term investments	175	193
Other investments:
Free-standing derivatives, assets	0	0
Separate account assets	3,488	3,639
Other assets	0	1
Total assets at fair value	5,432	5,858
Other liabilities:
Free-standing derivatives, liabilities	0	0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | U.S. government and agencies
Assets
Fixed income securities	484	546
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | Municipal
Assets
Fixed income securities	0	0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | Corporate - public
Assets
Fixed income securities	0	0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | Corporate - privately placed
Assets
Fixed income securities	0	0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | Foreign government
Assets
Fixed income securities	0	0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | ABS - CDO
Assets
Fixed income securities	0	0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | ABS - consumer and other
Assets
Fixed income securities	0	0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | RMBS
Assets
Fixed income securities	0	0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | CMBS
Assets
Fixed income securities	0	0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | Redeemable preferred stock
Assets
Fixed income securities	0	0
Recurring basis | Significant other observable inputs (Level 2)
Assets
Fixed income securities	23,265	23,417
Equity securities	3	3
Short-term investments	1,370	623
Other investments:
Free-standing derivatives, assets	60	59
Separate account assets	0	0
Other assets	0	0
Total assets at fair value	24,698	24,102
Other liabilities:
Free-standing derivatives, liabilities	(16)	(7)
Recurring basis | Significant other observable inputs (Level 2) | U.S. government and agencies
Assets
Fixed income securities	440	431
Recurring basis | Significant other observable inputs (Level 2) | Municipal
Assets
Fixed income securities	2,405	2,364
Recurring basis | Significant other observable inputs (Level 2) | Corporate - public
Assets
Fixed income securities	12,447	12,490
Recurring basis | Significant other observable inputs (Level 2) | Corporate - privately placed
Assets
Fixed income securities	5,429	5,523
Recurring basis | Significant other observable inputs (Level 2) | Foreign government
Assets
Fixed income securities	379	384
Recurring basis | Significant other observable inputs (Level 2) | ABS - CDO
Assets
Fixed income securities	157	178
Recurring basis | Significant other observable inputs (Level 2) | ABS - consumer and other
Assets
Fixed income securities	1,161	1,145
Recurring basis | Significant other observable inputs (Level 2) | RMBS
Assets
Fixed income securities	415	451
Recurring basis | Significant other observable inputs (Level 2) | CMBS
Assets
Fixed income securities	417	436
Recurring basis | Significant other observable inputs (Level 2) | Redeemable preferred stock
Assets
Fixed income securities	15	15
Recurring basis | Significant unobservable inputs (Level 3)
Assets
Fixed income securities	694	666
Equity securities	56	60
Short-term investments	0	0
Other investments:
Free-standing derivatives, assets	1	1
Separate account assets	0	0
Other assets	1	1
Total assets at fair value	752	728
Other liabilities:
Free-standing derivatives, liabilities	(9)	(8)
Recurring basis | Significant unobservable inputs (Level 3) | U.S. government and agencies
Assets
Fixed income securities	0	0
Recurring basis | Significant unobservable inputs (Level 3) | Municipal
Assets
Fixed income securities	66	78
Recurring basis | Significant unobservable inputs (Level 3) | Corporate - public
Assets
Fixed income securities	38	44
Recurring basis | Significant unobservable inputs (Level 3) | Corporate - privately placed
Assets
Fixed income securities	497	447
Recurring basis | Significant unobservable inputs (Level 3) | Foreign government
Assets
Fixed income securities	0	0
Recurring basis | Significant unobservable inputs (Level 3) | ABS - CDO
Assets
Fixed income securities	50	53
Recurring basis | Significant unobservable inputs (Level 3) | ABS - consumer and other
Assets
Fixed income securities	43	44
Recurring basis | Significant unobservable inputs (Level 3) | RMBS
Assets
Fixed income securities	0	0
Recurring basis | Significant unobservable inputs (Level 3) | CMBS
Assets
Fixed income securities	0	0
Recurring basis | Significant unobservable inputs (Level 3) | Redeemable preferred stock
Assets
Fixed income securities	$ 0	0
Non-recurring basis
Other investments:
Derivative asset, fair value, gross liability and obligation to return cash, offset
Non-recurring basis | Quoted prices in active markets for identical assets (Level 1)
Other investments:
Total assets at fair value	$ 0	0
Non-recurring basis | Significant other observable inputs (Level 2)
Other investments:
Total assets at fair value	0	0
Non-recurring basis | Significant unobservable inputs (Level 3)
Other investments:
Total assets at fair value	24	8
Contractholder funds: Derivatives embedded in life and annuity contracts | Recurring basis | Quoted prices in active markets for identical assets (Level 1)
Contract holder funds:
Derivatives embedded in life and annuity contracts	0	0
Contractholder funds: Derivatives embedded in life and annuity contracts | Recurring basis | Significant other observable inputs (Level 2)
Contract holder funds:
Derivatives embedded in life and annuity contracts	0	0
Contractholder funds: Derivatives embedded in life and annuity contracts | Recurring basis | Significant unobservable inputs (Level 3)
Contract holder funds:
Derivatives embedded in life and annuity contracts	(313)	(299)
Fair value
Other investments:
Total assets at fair value	$ 30,897	$ 30,685
% of total assets at fair value	100.00%	100.00%
Limited partnership interests	$ 20	$ 3
Other liabilities:
Total liabilities at fair value	$ (337)	$ (313)
% of total liabilities at fair value	100.00%	100.00%
Fair value | Recurring basis
Assets
Fixed income securities	$ 24,443	$ 24,629
Equity securities	1,344	1,542
Short-term investments	1,545	816
Other investments:
Free-standing derivatives, assets	52	49
Separate account assets	3,488	3,639
Other assets	1	2
Total assets at fair value	30,873	30,677
Other liabilities:
Free-standing derivatives, liabilities	(24)	(14)
Fair value | Recurring basis | U.S. government and agencies
Assets
Fixed income securities	924	977
Fair value | Recurring basis | Municipal
Assets
Fixed income securities	2,471	2,442
Fair value | Recurring basis | Corporate - public
Assets
Fixed income securities	12,485	12,534
Fair value | Recurring basis | Corporate - privately placed
Assets
Fixed income securities	5,926	5,970
Fair value | Recurring basis | Foreign government
Assets
Fixed income securities	379	384
Fair value | Recurring basis | ABS - CDO
Assets
Fixed income securities	207	231
Fair value | Recurring basis | ABS - consumer and other
Assets
Fixed income securities	1,204	1,189
Fair value | Recurring basis | RMBS
Assets
Fixed income securities	415	451
Fair value | Recurring basis | CMBS
Assets
Fixed income securities	417	436
Fair value | Recurring basis | Redeemable preferred stock
Assets
Fixed income securities	15	15
Fair value | Non-recurring basis
Other investments:
Total assets at fair value	24	8
Fair value | Contractholder funds: Derivatives embedded in life and annuity contracts | Recurring basis
Contract holder funds:
Derivatives embedded in life and annuity contracts	(313)	(299)
Fixed Income Securities Valued Based on Nonbinding Broker Quotes [Member] | Significant unobservable inputs (Level 3)
Other investments:
Total assets at fair value	$ 587	$ 577