Share-Based Compensation (Narrative) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Number of stock options granted	21.8
Number of restricted share units granted	5.7
Weighted average fair value of stock options granted	$ 7.38
Fair value of restricted share units granted	$ 27.43
Stock Options [Member]
Unrecognized pretax compensation expense on nonvested awards	$ 417
Restricted Share Units [Member]
Unrecognized pretax compensation expense on nonvested awards	439
Employee Stock Purchase Plan [Member]
Cash received from exercise of stock options	$ 18	$ 15