Quarterly Operating Results (Unaudited) (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Operating Results (Unaudited) [Line Items]
Adverse prior year development in the property and transportation sub-segment	$ (10)	$ (13)	$ (14)	$ 31	$ 5	$ (40)	$ 22	$ 28	$ (6)	$ 15	$ 30
Property and Casualty Insurance [Member]
Quarterly Operating Results (Unaudited) [Line Items]
Special charges to increase asbestos and environmental reserves		24				54
Former Railroad and Manufacturing Operations [Member]
Quarterly Operating Results (Unaudited) [Line Items]
Special charges to increase asbestos and environmental reserves		6				22
Specialty Property and transportation [Member]
Quarterly Operating Results (Unaudited) [Line Items]
Adverse prior year development in the property and transportation sub-segment			$ (22)