Summary of Significant Accounting Policies (Narrative) (Details) (USD $) Share data in Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Loss on reinsurance transaction	$ 34,000,000
Business Acquisition, Purchase Price			231,000,000
Business Combination, Acquisition Related Costs			4,000,000
Anticipated amounts due from insureds related to losses under deductible policies	1,400,000,000	1,300,000,000
Minimum interest rate used in determining present value of obligations of structured settlements not funded by annuities	5.50%	7.10%
Maximum interest rate used in determining present value of obligations of structured settlements not funded by annuities	8.00%	9.70%
Discounted reserves for unfunded structured settlements	582,000,000	580,000,000
Discounted reserves for unfunded structure settlements, discount amount	924,000,000	969,000,000
Minimum interest rate used to discount workers' compensation lifetime claim reserves and accident and health claim reserves	3.50%	3.00%
Maximum interest rate used to discount workers' compensation lifetime claim reserves and accident and health claim reserves	6.80%	6.80%
Discounted reserves for worker's compensation lifetime claim reserves and accident and health claim reserves	2,500,000,000	2,400,000,000
Discounted reserves for worker's compensation lifetime claim reserves and accident and health claim reserves, discount amount	654,000,000	617,000,000
Minimum interest rate used to calculate reserves for long term care products	4.50%	4.50%
Maximum interest rate used to calculate reserves for payout annuity contracts	7.90%	7.90%
Minimum interest rate used to calculate reserves for payout annuity contracts		5.00%
Maximum interest rate used to calculate reserves for payout annuity contracts		8.70%
Liability balance for guaranty fund	131,000,000	143,000,000
Percentage of billed receivables compared to total reinsurance receivables	5% or less
Deposit assets	3,000,000	3,000,000
Deposit liabilities	9,000,000	130,000,000
Deferred acquisition costs, net of shadow adjustment	314,000,000	342,000,000
Investments in life settlement contracts	82,000,000	88,000,000
Increase (decrease) in fair value recognized on life settlement contracts	8,000,000	(2,000,000)	11,000,000
Gain recognized on matured life settlement contracts	25,000,000	15,000,000	42,000,000
Decrease in shadow adjustment, net of tax		979,000,000
Increase in shadow adjustment, net of tax	756,000,000
Reduction of net unrealized gains on investments included in AOCI due to shadow adjustments	1,288,000,000	532,000,000
Foreign currency transaction gain (loss), before tax	(25,000,000)	2,000,000	12,000,000
Weighted average number diluted shares outstanding adjustment	675	552	417
Antidilutive securities excluded from computation of earnings per share, amount	170	111	730
Interest paid, net	179,000,000	164,000,000	170,000,000
Proceeds from income tax refunds			29,000,000
Income taxes paid	$ 313,000,000	$ 129,000,000
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] | Software [Member]
Property, Plant and Equipment, Useful Life	3 years
Maximum [Member]
Requisite service period for stock- based compensation expense	4 years
Maximum [Member] | Software [Member]
Property, Plant and Equipment, Useful Life	5 years
Property and Casualty insurance core operations [Member]
Number of Operating Segments	3
Life and Group Non-Core & Corporate and Other Non-Core operations [Member]
Number of Operating Segments	2