Consolidated Statements of Changes in Shareholders' Equity (USD $) In Millions, except Share data in Thousands, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated other comprehensive income (loss) [Member]	Noncontrolling Interests [Member]
Beginning balance, Value at Dec. 31, 2010	$ 16,498	$ 3,472	$ 5,776	$ 7,935	$ (747)	$ 62
Beginning balance, Shares at Dec. 31, 2010		694,381
Comprehensive income (loss):
Net income	234			225		9
Net change in other comprehensive income (loss)	41				41
Stock transactions:
In connection with equity award, Shares		1,763
In connection with equity awards, Values	1	9	(8)
Shares repurchased in connection with equity awards, Shares		(595)
Shares repurchased in connection with equity awards, Value	(17)	(3)	(14)
In connection with dividend reinvestment plan, Shares		274
In connection with dividend reinvestment plan, Value	7	1	6
In connection with 401(k) plan, Shares		462
In connection with 401(k) plan, Value	13	2	11
Cash dividends declared on common stock	(118)			(118)
Equity-based compensation expense	24		24
Other, net	(13)		(1)			(12)
Ending balance, Value at Mar. 31, 2011	16,670	3,481	5,794	8,042	(706)	59
Ending balance, Shares at Mar. 31, 2011		696,285
Beginning balance, Value at Dec. 31, 2011	17,480	3,486	5,873	8,772	(713)	62
Beginning balance, Shares at Dec. 31, 2011		697,143
Comprehensive income (loss):
Net income	445			431		14
Net change in other comprehensive income (loss)	97				97
Stock transactions:
In connection with equity awards, Shares		1,794
In connection with equity awards, Values	6	9	(3)
Shares repurchased in connection with equity awards, Shares		(497)
Shares repurchased in connection with equity awards, Value	(15)	(3)	(12)
In connection with dividend reinvestment plan, Shares		14
Cash dividends declared on common stock	(140)			(140)
Equity-based compensation expense	25		25
Other, net	(16)		(3)	1		(14)
Ending balance, Value at Mar. 31, 2012	$ 17,882	$ 3,492	$ 5,880	$ 9,064	$ (616)	$ 62
Ending balance, Shares at Mar. 31, 2012		698,454