Aquisitions and Sales of Subsidiaries (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended		1 Months Ended	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2012	Dec. 31, 2010	Jul. 31, 2010	Aug. 31, 2012 Medicare supplement and critical illness businesses [Member]	Sep. 30, 2012 Small Annuity and Supplemental Insurance Company [Member]	Mar. 31, 2011 National Interstate [Member]	Jul. 31, 2010 National Interstate [Member]	Dec. 31, 2012 Vanliner Group, Inc. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage ownership of National Interstate			52.00%
Purchase of subsidiaries including post-closing adjustments						$ 114
Period of Balance Sheet guarantee							4 years 6 months
Gain on bargain purchase		7
Premiums associated with policies in force								107
Sale proceeds				326	7
Pretax gain on sale of subsidiaries				170
Percentage of interest acquired in a subsidiary	28.00%
Purchase of interest not already owned in a subsidiary	$ 17