Goodwill (details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Goodwill by segment
Goodwill	$ 3,588	$ 3,573
Reportable Segments [Member] | Business and International Insurance [Member]
Goodwill by segment
Goodwill	2,454	2,439
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