Condensed Consolidated Statements of Changes in Common Shareholders' Equity (Unaudited) (USD $) In Millions, except Share data, unless otherwise specified	Total USD ($)		Common Shares (Units) [Member]	Treasury Shares (Units) [Member]	Common Shares [Member] USD ($)	Paid-in-Surplus [Member] USD ($)	Retained Earnings [Member] USD ($)	Treasury Shares [Member] USD ($)	Accumulated Other Comprehensive Loss (Note 9) [Member] USD ($)
Shareholders' equity, beginning balance at Dec. 31, 2011	$ 18,578				$ 1,386	$ 4,031	$ 19,508	$ (5,293)	$ (1,054)
Common shares, beginning balance at Dec. 31, 2011			554,300,000	(74,400,000)
Comprehensive income [Abstract]
Net income	863				0	0	863	0	0
Other comp. income	8	[1]			0	0	0	0	8	[1]
Conversion, stock option exercises, forfeitures, and other	26				1	25	0	0	0
Conversion, stock option exercises, forfeitures, and other (shares)			300,000	600,000
Share repurchases (Note 17)	(433)				0	0	0	(433)	0
Share repurchases (Note 17) (shares)	(3,917,369)		0	(3,900,000)
Cash dividends declared	(287)				0	0	(287)	0	0
Shareholders' equity, ending balance at Mar. 31, 2012	18,755				1,387	4,056	20,084	(5,726)	(1,046)
Common shares, ending balance at Mar. 31, 2012			554,600,000	(77,700,000)
Shareholders' equity, beginning balance at Dec. 31, 2012	19,877				1,386	4,113	22,271	(6,707)	(1,186)
Common shares, beginning balance at Dec. 31, 2012	469,465,273		554,600,000	(85,100,000)
Comprehensive income [Abstract]
Net income	957				0	0	957	0	0
Other comp. income	17	[1]			0	0	0	0	17	[1]
Conversion, stock option exercises, forfeitures, and other	10				1	21	0	(12)	0
Conversion, stock option exercises, forfeitures, and other (shares)			200,000	300,000
Share repurchases (Note 17)	(394)				0	0	0	(394)	0
Share repurchases (Note 17) (shares)	(2,881,400)		0	(2,900,000)
Cash dividends declared	(323)				0	0	(323)	0	0
Shareholders' equity, ending balance at Mar. 31, 2013	$ 20,144				$ 1,387	$ 4,134	$ 22,905	$ (7,113)	$ (1,169)
Common shares, ending balance at Mar. 31, 2013	467,137,922		554,800,000	(87,700,000)

[1] Net of deferred taxes of $12 million and $8 million during the three months ended March 31, 2013 and 2012, respectively.