Consolidated Statements of Shareholders' Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement Of Comprehensive Income [Abstract]
Shareholders' Net Income	$ 588	$ 573	$ 1,121	$ 1,101
Shareholders' other comprehensive income (loss):
Net unrealized appreciation (depreciation) on securities	(234)	103	(146)	189
Net unrealized appreciation (depreciation), derivatives	5	0	12	0
Net translation of foreign currencies	18	46	(86)	35
Postretirement benefits liability adjustment	20	11	31	23
Shareholders' other comprehensive income (loss)	(191)	160	(189)	247
Shareholders' comprehensive income (loss)	$ 397	$ 733	$ 932	$ 1,348