Fair Value of Assets and Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Assets
Fixed income securities	$ 23,696	$ 24,222
Equity securities	1,589	1,511
Short-term investments	760	566
Other investments: Free-standing derivatives	1		$ 1
Separate account assets	3,417	3,373
Derivative asset, fair value, gross liability and obligation to return cash, offset	$ (7)	$ (6)
% of total assets at fair value	0.00%	0.00%
Liabilities
Other liabilities: Free-standing derivatives	$ (2)		$ (9)
Free standing derivative liabilities derivative liability, fair value, gross asset and right to reclaim cash, offset	$ 3	$ 2
% of total liabilities at fair value	(0.90%)	(0.60%)
Other investments	$ 1
U.S. government and agencies
Assets
Fixed income securities	634	$ 1,014
Municipal
Assets
Fixed income securities	2,266	2,274
Foreign government
Assets
Fixed income securities	327	332
RMBS
Assets
Fixed income securities	301	333
CMBS
Assets
Fixed income securities	179	241
Redeemable preferred stock
Assets
Fixed income securities	15	16
Quoted prices in active markets for identical assets (Level 1)
Assets
Total assets at fair value	$ 5,343	$ 5,590
% of total assets at fair value	18.10%	18.70%
Liabilities
Total liabilities at fair value	$ 0	$ 0
% of total liabilities at fair value	0.00%	0.00%
Significant other observable inputs (Level 2)
Assets
Total assets at fair value	$ 23,704	$ 23,668
% of total assets at fair value	80.10%	79.50%
Liabilities
Total liabilities at fair value	$ (46)	$ (39)
% of total liabilities at fair value	13.90%	11.90%
Significant unobservable inputs (Level 3)
Assets
Total assets at fair value	$ 532	$ 526
% of total assets at fair value	1.80%	1.80%
Liabilities
Total liabilities at fair value	$ (287)	$ (292)
% of total liabilities at fair value	87.00%	88.70%
Recurring basis
Assets
Other investments: Free-standing derivatives, gross liability and obligation to return cash, offset	$ (7)	$ (6)
Derivative asset, fair value, gross liability and obligation to return cash, offset	(7)	(6)
Liabilities
Free standing derivative liabilities derivative liability, fair value, gross asset and right to reclaim cash, offset	3	2
Recurring basis | Quoted prices in active markets for identical assets (Level 1)
Assets
Fixed income securities	259	619
Equity securities	1,505	1,432
Short-term investments	162	166
Other investments: Free-standing derivatives	0	0
Separate account assets	3,417	3,373
Other assets		0
Total assets at fair value	5,343	5,590
Liabilities
Other liabilities: Free-standing derivatives	0	0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | U.S. government and agencies
Assets
Fixed income securities	259	619
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	22,994	23,164
Equity securities	4	3
Short-term investments	598	400
Other investments: Free-standing derivatives	108	101
Separate account assets	0	0
Other assets		0
Total assets at fair value	23,704	23,668
Liabilities
Other liabilities: Free-standing derivatives	(46)	(39)
Recurring basis | Significant other observable inputs (Level 2) | U.S. government and agencies
Assets
Fixed income securities	375	395
Recurring basis | Significant other observable inputs (Level 2) | Municipal
Assets
Fixed income securities	2,206	2,215
Recurring basis | Significant other observable inputs (Level 2) | Corporate - public
Assets
Fixed income securities	13,457	13,475
Recurring basis | Significant other observable inputs (Level 2) | Corporate - privately placed
Assets
Fixed income securities	5,811	5,895
Recurring basis | Significant other observable inputs (Level 2) | Foreign government
Assets
Fixed income securities	327	332
Recurring basis | Significant other observable inputs (Level 2) | ABS - CDO
Assets
Fixed income securities	77	102
Recurring basis | Significant other observable inputs (Level 2) | ABS - consumer and other
Assets
Fixed income securities	246	160
Recurring basis | Significant other observable inputs (Level 2) | RMBS
Assets
Fixed income securities	301	333
Recurring basis | Significant other observable inputs (Level 2) | CMBS
Assets
Fixed income securities	179	241
Recurring basis | Significant other observable inputs (Level 2) | Redeemable preferred stock
Assets
Fixed income securities	15	16
Recurring basis | Significant unobservable inputs (Level 3)
Assets
Fixed income securities	443	439
Equity securities	80	76
Short-term investments	0	0
Other investments: Free-standing derivatives	1	1
Separate account assets	0	0
Other assets		1
Total assets at fair value	524	517
Liabilities
Other liabilities: Free-standing derivatives	(2)	(3)
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	60	59
Recurring basis | Significant unobservable inputs (Level 3) | Corporate - public
Assets
Fixed income securities	36	47
Recurring basis | Significant unobservable inputs (Level 3) | Corporate - privately placed
Assets
Fixed income securities	268	264
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	32	27
Recurring basis | Significant unobservable inputs (Level 3) | ABS - consumer and other
Assets
Fixed income securities	47	42
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 | Quoted prices in active markets for identical assets (Level 1)
Assets
Total assets at fair value	0	0
Non-recurring basis | Significant other observable inputs (Level 2)
Assets
Total assets at fair value	0	0
Non-recurring basis | Significant unobservable inputs (Level 3)
Assets
Total assets at fair value	8	9
Contractholder funds: Derivatives embedded in life and annuity contracts | Recurring basis | Quoted prices in active markets for identical assets (Level 1)
Liabilities
Contractholder 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)
Liabilities
Contractholder 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)
Liabilities
Contractholder funds: Derivatives embedded in life and annuity contracts	(285)	(289)
Fair value
Assets
Total assets at fair value	$ 29,572	$ 29,778
% of total assets at fair value	100.00%	100.00%
Liabilities
Total liabilities at fair value	$ (330)	$ (329)
% of total liabilities at fair value	100.00%	100.00%
Limited partnership interests	$ 7	$ 9
Fair value | Recurring basis
Assets
Fixed income securities	23,696	24,222
Equity securities	1,589	1,511
Short-term investments	760	566
Other investments: Free-standing derivatives	102	96
Separate account assets	3,417	3,373
Other assets		1
Total assets at fair value	29,564	29,769
Liabilities
Other liabilities: Free-standing derivatives	(45)	(40)
Fair value | Recurring basis | U.S. government and agencies
Assets
Fixed income securities	634	1,014
Fair value | Recurring basis | Municipal
Assets
Fixed income securities	2,266	2,274
Fair value | Recurring basis | Corporate - public
Assets
Fixed income securities	13,493	13,522
Fair value | Recurring basis | Corporate - privately placed
Assets
Fixed income securities	6,079	6,159
Fair value | Recurring basis | Foreign government
Assets
Fixed income securities	327	332
Fair value | Recurring basis | ABS - CDO
Assets
Fixed income securities	109	129
Fair value | Recurring basis | ABS - consumer and other
Assets
Fixed income securities	293	202
Fair value | Recurring basis | RMBS
Assets
Fixed income securities	301	333
Fair value | Recurring basis | CMBS
Assets
Fixed income securities	179	241
Fair value | Recurring basis | Redeemable preferred stock
Assets
Fixed income securities	15	16
Fair value | Non-recurring basis
Assets
Total assets at fair value	8	9
Fair value | Contractholder funds: Derivatives embedded in life and annuity contracts | Recurring basis
Liabilities
Contractholder funds: Derivatives embedded in life and annuity contracts	$ (285)	$ (289)