Goodwill (details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Goodwill by segment
Goodwill	$ 3,579	$ 3,611
Reportable Segments [Member] | Business and International Insurance [Member]
Goodwill by segment
Goodwill	2,443	2,476
Reportable Segments [Member] | Bond & Specialty Insurance [Member]
Goodwill by segment
Goodwill	496	495
Reportable Segments [Member] | Personal Insurance [Member]
Goodwill by segment
Goodwill	612	613
Other [Member]
Goodwill by segment
Goodwill	$ 28	$ 27