Investments (Fixed Maturity and Equity Securities Available-For-Sale by Sector) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	$ 49,312	$ 50,154
Cost or Amortized Cost	280	384
Gross Unrealized OTTI Loss	1	(19)	$ (34)
Available-for-sale Securities, Debt Securities	51,785	52,409
Equity securities	300	409
Fixed Maturity Securities
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	49,312	50,154
Gross Unrealized Gain	3,227	3,089
Gross Unrealized Temporary Loss	755	815
Gross Unrealized OTTI Loss	(1)	19
Available-for-sale Securities, Debt Securities	51,785	52,409
U.S. corporate
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	17,583	16,160
Gross Unrealized Gain	1,158	979
Gross Unrealized Temporary Loss	235	393
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	18,506	16,746
U.S. government and agency
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	10,517	12,562
Gross Unrealized Gain	1,221	1,297
Gross Unrealized Temporary Loss	188	53
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	11,550	13,806
RMBS
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	6,722	8,391
Gross Unrealized Gain	194	201
Gross Unrealized Temporary Loss	101	95
Gross Unrealized OTTI Loss	0	19
Available-for-sale Securities, Debt Securities	6,815	8,478
Foreign corporate
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	5,512	4,995
Gross Unrealized Gain	201	153
Gross Unrealized Temporary Loss	158	194
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	5,555	4,954
State and political subdivision
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	2,633	2,398
Gross Unrealized Gain	305	321
Gross Unrealized Temporary Loss	24	13
Gross Unrealized OTTI Loss	0	1
Available-for-sale Securities, Debt Securities	2,914	2,705
CMBS
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	2,837	2,303
Gross Unrealized Gain	26	20
Gross Unrealized Temporary Loss	26	23
Gross Unrealized OTTI Loss	(1)	(1)
Available-for-sale Securities, Debt Securities	2,838	2,301
ABS
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	2,562	2,694
Gross Unrealized Gain	11	14
Gross Unrealized Temporary Loss	12	34
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	2,561	2,674
Foreign government
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	946	651
Gross Unrealized Gain	111	104
Gross Unrealized Temporary Loss	11	10
Gross Unrealized OTTI Loss	0	0
Available-for-sale Securities, Debt Securities	1,046	745
Equity securities
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	280	384
Gross Unrealized Gain	29	39
Gross Unrealized Temporary Loss	9	14
Gross Unrealized OTTI Loss	0	0
Equity securities	300	409
Non-redeemable preferred stock
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	180	217
Gross Unrealized Gain	6	16
Gross Unrealized Temporary Loss	9	9
Gross Unrealized OTTI Loss	0	0
Equity securities	177	224
Common Stock
Available-for-sale Securities [Abstract]
Cost or Amortized Cost	100	167
Gross Unrealized Gain	23	23
Gross Unrealized Temporary Loss	0	5
Gross Unrealized OTTI Loss	0	0
Equity securities	$ 123	$ 185

Other-than-temporary impairments on fixed maturity securities transferred to other comprehensive income loss.

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Other-than-temporary impairments on equity securities transferred to other comprehensive loss.

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This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount of debt securities categorized neither as held-to-maturity nor trading.

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