Quarterly Operating Results (Unaudited) (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended			12 Months Ended			3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Sep. 30, 2012 Property and Casualty Insurance [Member]	Jun. 30, 2011 Property and Casualty Insurance [Member]	Dec. 31, 2012 Medicare Supplement and Critical Illness [Member]	Sep. 30, 2012 Medicare Supplement and Critical Illness [Member]	Jun. 30, 2011 Railroad and Manufacturing Operations [Member]	Dec. 31, 2011 Investment in Verisk Analytics, Inc. [Member]	Jun. 30, 2011 Investment in Verisk Analytics, Inc. [Member]	Dec. 31, 2012 Settlement with Taxing Authority [Member]	Sep. 30, 2012 Settlement with Taxing Authority [Member]
Quarterly Operating Results Unaudited [Line Items]
Realized gains (losses) on subsidiaries				$ 161	$ (3)	$ (13)			$ 15	$ 155
Quarterly Operating Results (Unaudited) (Textual) [Abstract]
Special charges to increase asbestos and environmental reserves							31	50			9
Tax benefit related to settlement of litigation														39	28
Pretax charge on closed block of long-term care insurance	153
Pretax catastrophe losses	32		23
Pretax charge due to review of major actuarial assumptions in the annuity business	14
Realized gains (losses) on securities				210	76	101						40	33
Charge for valuation allowance against deferred tax assets		$ 34