CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net Income	$ 656	$ 506
Other Comprehensive Income (Loss), Net of Tax
Change in Unrealized Appreciation of Investments	4	54
Change in Unrealized Other-Than-Temporary Impairment Losses on Investments		1
Foreign Currency Translation Losses	(50)	(9)
Change in Postretirement Benefit Costs Not Yet Recognized in Net Income	17	14
Total Other Comprehensive Income (Loss) Net of Tax	(29)	60
Comprehensive Income	$ 627	$ 566