Consolidated Statements of Shareholders' Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement Of Comprehensive Income [Abstract]
Shareholders' Net Income	$ 547	$ 534	$ 1,668	$ 1,635
Shareholders' other comprehensive income (loss):
Net unrealized appreciation (depreciation) on securities	8	(49)	(138)	140
Net unrealized appreciation (depreciation), derivatives	3	6	15	6
Net translation of foreign currencies	(112)	(113)	(198)	(78)
Postretirement benefits liability adjustment	11	10	42	33
Shareholders' other comprehensive income (loss)	(90)	(146)	(279)	101
Shareholders' comprehensive income (loss)	$ 457	$ 388	$ 1,389	$ 1,736