Goodwill (details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Goodwill by segment
Goodwill	$ 3,573	$ 3,611
Reportable Segments [Member] | Business and International Insurance [Member]
Goodwill by segment
Goodwill	2,439	2,477
Reportable Segments [Member] | Bond & Specialty Insurance [Member]
Goodwill by segment
Goodwill	496	496
Reportable Segments [Member] | Personal Insurance [Member]
Goodwill by segment
Goodwill	612	612
Other [Member]
Goodwill by segment
Goodwill	$ 26	$ 26