Segments of Operations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Segment Reporting Information [Line Items]
Total premiums earned	$ 687		$ 603
Net investment income	326		317
Other income	22		18
Revenues before realized gains (losses)	1,091		1,043
Realized gains on securities	57		44
Total revenues	1,148		1,087
Property and Casualty Insurance [Member]
Segment Reporting Information [Line Items]
Net investment income	66		70
Other income	3		3
Revenues before realized gains (losses)	756		676
Annuity [Member]
Segment Reporting Information [Line Items]
Net investment income	248		228
Other income	14		13
Revenues before realized gains (losses)	262		241
Run-off Long-term Care and Life [Member]
Segment Reporting Information [Line Items]
Revenues before realized gains (losses)	50		47
Medicare Supplement and Critical Illness [Member]
Segment Reporting Information [Line Items]
Revenues before realized gains (losses)		[1]	80	[1]
Other [Member]
Segment Reporting Information [Line Items]
Revenues before realized gains (losses)	23		(1)
Specialty Property and transportation [Member]
Segment Reporting Information [Line Items]
Total premiums earned	293		263
Specialty casualty [Member]
Segment Reporting Information [Line Items]
Total premiums earned	259		220
Specialty financial [Member]
Segment Reporting Information [Line Items]
Total premiums earned	116		103
Specialty Other [Member]
Segment Reporting Information [Line Items]
Total premiums earned	$ 19		$ 17

[1] Sold in August 2012.