Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loss on reinsurance transaction			$ 34
Anticipated amounts due from insureds related to losses under deductible policies	$ 1,200	$ 1,200
Structured Settlement Annuities, Interest Rate, Low End	5.50%	5.50%
Structured Settlement Annuities, Interest Rates, High End	8.00%	8.00%
Discounted reserves for unfunded structured settlements	$ 544	$ 560
Discounted reserves for unfunded structure settlements, discount amount	841	880
Amount of interest recognized on the discounted reserves of unfunded structured settlements	$ 42	$ 42	43
Interest rates at which workers' compensation lifetime claim reserves are discounted at	3.50%	3.50%
Workers' Compensation Liability	$ 371	$ 396
Discounted reserves for workers’ compensation lifetime claim reserves, discount amount	202	218
Amount of interest accretion recognized on the discounted reserves of workers’ compensation lifetime claim reserves	$ 17	$ 20	22
Minimum interest rate used to discount long term care claim reserves	4.50%	4.50%
Maximum interest rate used to discount long term care claim reserves	6.80%	6.80%
Discounted reserves for long term care claim reserves	$ 2,200	$ 2,200
Discounted reserves for long term care claim reserves, discount amount	$ 529	435
Long term care premium deficiency		296
Write off of deferred acquisition cost asset due to long term care premium deficiency		289
Adjustment to Active life reserves due to premium deficiency		7
Minimum interest rate used to calculate reserves for long term care products	6.60%
Maximum interest rate used to calculate reserves for long term care products	7.00%
Liability balance for guaranty fund	$ 125	129
Percentage of billed receivables compared to total reinsurance receivables	3% or less
Deposit assets	$ 3	3
Deposit liabilities	6	8
Loss on life settlement contracts, held for sale	10
Investments in life settlement contracts	58	74
Increase in fair value recognized on life settlement contracts	7	1	8
Gain recognized on matured life settlement contracts	8	24	25
Decreased Net Investment Income and amortized cost of fixed maturity securities due to a change in estimate effected by a change in accounting principle		39
Decreased Net Investment Income and amortized cost of fixed maturity securities due to a change in estimate effected by a change in accounting principle relating to 2014 and prior		$ 22
Decrease of Basic and Diluted Earnings per Share due to change in estimate effected by a change in accounting principle		$ 0.09
Decrease in shadow adjustment, net of tax	97	$ 177
Reduction of net unrealized gains on investments included in AOCI due to shadow adjustments	1,014	1,111
Foreign currency transaction gain (loss), before tax	$ (9)	$ (11)	$ (25)
Weighted average number diluted shares outstanding adjustment	678	534	675
Antidilutive securities excluded from computation of earnings per share, amount	102	106	170
Interest paid, net	$ 157	$ 152	$ 179
Income taxes paid	170	310	$ 313
Cumulative Effect of New Accounting Principle in Period of Adoption on Long Term Debt		(2)
Cumulative Effect of New Accounting Principle in Period of Adoption on Other Assets		(2)
Other Invested Assets Overseas Deposit	31	27
Limited partnership investments	$ 2,371	2,548
Furniture and Fixtures [Member]
Property, Plant and Equipment, Useful Life	7 years
Office Equipment [Member]
Property, Plant and Equipment, Useful Life	5 years
Building and Building Improvements [Member]
Property, Plant and Equipment, Useful Life	50 years
Minimum [Member]
Requisite service period for stock- based compensation expense	3 years
Minimum [Member] | Computer Software, Intangible Asset [Member]
Property, Plant and Equipment, Useful Life	3 years
Maximum [Member]
Requisite service period for stock- based compensation expense	4 years
Maximum [Member] | Computer Software, Intangible Asset [Member]
Property, Plant and Equipment, Useful Life	10 years
Pension Plans, Defined Benefit [Member]
Limited partnership investments	$ 876	$ 935