Fair Value of Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets
Fixed income securities	$ 24,222	$ 24,629
Equity securities	1,511	1,542
Short-term investments	566	816
Other investments:
Other investments: Free-standing derivatives	1	1	$ 2
Separate account assets	3,373	3,639
Derivative asset, fair value	$ (6)	$ (11)
% of total assets at fair value	0.00%	0.00%
Liabilities
Other liabilities: Free-standing derivatives	$ (3)	$ (8)	$ (9)
Total liabilities at fair value, Counterparty and cash collateral netting		$ 1
% of total liabilities at fair value	(0.60%)	(0.30%)
U.S. government and agencies
Assets
Fixed income securities	$ 1,014	$ 977
Municipal
Assets
Fixed income securities	2,274	2,442
Foreign government
Assets
Fixed income securities	332	384
RMBS
Assets
Fixed income securities	333	451
CMBS
Assets
Fixed income securities	241	436
Redeemable preferred stock
Assets
Fixed income securities	16	15
Quoted prices in active markets for identical assets (Level 1)
Other investments:
Total assets at fair value	$ 5,590	$ 5,858
% of total assets at fair value	18.70%	19.10%
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	$ 23,668	$ 24,102
% of total assets at fair value	79.50%	78.50%
Liabilities
Total liabilities at fair value	$ (39)	$ (7)
% of total liabilities at fair value	11.90%	2.20%
Significant unobservable inputs (Level 3)
Other investments:
Total assets at fair value	$ 526	$ 736
% of total assets at fair value	1.80%	2.40%
Liabilities
Total liabilities at fair value	$ (292)	$ (307)
% of total liabilities at fair value	88.70%	98.10%
Recurring basis
Other investments:
Counterparty and cash collateral netting	$ (6)	$ (11)
Separate account assets		0
Derivative asset, fair value	(6)	(11)
Liabilities
Counterparty and cash collateral netting	2	1
Total liabilities at fair value, Counterparty and cash collateral netting	2
Recurring basis | Quoted prices in active markets for identical assets (Level 1)
Assets
Fixed income securities	619	546
Equity securities	1,432	1,479
Short-term investments	166	193
Other investments:
Other investments: Free-standing derivatives	0	0
Separate account assets		3,639
Other assets	0	1
Total assets at fair value	5,590	5,858
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	619	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	23,164	23,417
Equity securities	3	3
Short-term investments	400	623
Other investments:
Other investments: Free-standing derivatives	101	59
Separate account assets	0
Other assets	0	0
Total assets at fair value	23,668	24,102
Liabilities
Other liabilities: Free-standing derivatives	(39)	(7)
Recurring basis | Significant other observable inputs (Level 2) | U.S. government and agencies
Assets
Fixed income securities	395	431
Recurring basis | Significant other observable inputs (Level 2) | Municipal
Assets
Fixed income securities	2,215	2,364
Recurring basis | Significant other observable inputs (Level 2) | Corporate - public
Assets
Fixed income securities	13,475	12,490
Recurring basis | Significant other observable inputs (Level 2) | Corporate - privately placed
Assets
Fixed income securities	5,895	5,523
Recurring basis | Significant other observable inputs (Level 2) | Foreign government
Assets
Fixed income securities	332	384
Recurring basis | Significant other observable inputs (Level 2) | ABS - CDO
Assets
Fixed income securities	102	178
Recurring basis | Significant other observable inputs (Level 2) | ABS - consumer and other
Assets
Fixed income securities	160	1,145
Recurring basis | Significant other observable inputs (Level 2) | RMBS
Assets
Fixed income securities	333	451
Recurring basis | Significant other observable inputs (Level 2) | CMBS
Assets
Fixed income securities	241	436
Recurring basis | Significant other observable inputs (Level 2) | Redeemable preferred stock
Assets
Fixed income securities	16	15
Recurring basis | Significant unobservable inputs (Level 3)
Assets
Fixed income securities	439	666
Equity securities	76	60
Short-term investments	0	0
Other investments:
Other investments: Free-standing derivatives	1	1
Separate account assets	0	0
Other assets	1	1
Total assets at fair value	517	728
Liabilities
Other liabilities: Free-standing derivatives	(3)	(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	59	78
Recurring basis | Significant unobservable inputs (Level 3) | Corporate - public
Assets
Fixed income securities	47	44
Recurring basis | Significant unobservable inputs (Level 3) | Corporate - privately placed
Assets
Fixed income securities	264	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	27	53
Recurring basis | Significant unobservable inputs (Level 3) | ABS - consumer and other
Assets
Fixed income securities	42	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 | 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	9	8
Fair value
Other investments:
Total assets at fair value	$ 29,778	$ 30,685
% of total assets at fair value	100.00%	100.00%
Limited partnership interests	$ 9	$ 3
Other investments		5
Liabilities
Total liabilities at fair value	$ (329)	$ (313)
% of total liabilities at fair value	100.00%	100.00%
Fair value | Recurring basis
Assets
Fixed income securities	$ 24,222	$ 24,629
Equity securities	1,511	1,542
Short-term investments	566	816
Other investments:
Other investments: Free-standing derivatives	96	49
Separate account assets	3,373	3,639
Other assets	1	2
Total assets at fair value	29,769	30,677
Liabilities
Other liabilities: Free-standing derivatives	(40)	(14)
Fair value | Recurring basis | U.S. government and agencies
Assets
Fixed income securities	1,014	977
Fair value | Recurring basis | Municipal
Assets
Fixed income securities	2,274	2,442
Fair value | Recurring basis | Corporate - public
Assets
Fixed income securities	13,522	12,534
Fair value | Recurring basis | Corporate - privately placed
Assets
Fixed income securities	6,159	5,970
Fair value | Recurring basis | Foreign government
Assets
Fixed income securities	332	384
Fair value | Recurring basis | ABS - CDO
Assets
Fixed income securities	129	231
Fair value | Recurring basis | ABS - consumer and other
Assets
Fixed income securities	202	1,189
Fair value | Recurring basis | RMBS
Assets
Fixed income securities	333	451
Fair value | Recurring basis | CMBS
Assets
Fixed income securities	241	436
Fair value | Recurring basis | Redeemable preferred stock
Assets
Fixed income securities	16	15
Fair value | Non-recurring basis
Other investments:
Total assets at fair value	9	8
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	(289)	(299)
Contractholder funds: Derivatives embedded in life and annuity contracts | Fair value | Recurring basis
Liabilities
Contractholder funds: Derivatives embedded in life and annuity contracts	$ (289)	$ (299)