Net Income per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]
Net income	$ 850	$ 689	$ 640	$ 677	$ 751	$ 597	$ 692	$ 570	$ 2,856	$ 2,609	$ 3,229
Denominator:
Weighted average common shares - basic	1,295	1,295	1,297	1,295	1,294	1,292	1,291	1,288	1,295	1,292	1,293
Dilutive effect of equity incentive plans									18	21	20
Weighted average common shares - diluted	1,310	1,310	1,313	1,319	1,318	1,314	1,309	1,308	1,313	1,313	1,313
Net income per share:
Basic	$ 0.66	$ 0.53	$ 0.49	$ 0.52	$ 0.58	$ 0.46	$ 0.54	$ 0.44	$ 2.20	$ 2.02	$ 2.50
Diluted	$ 0.65	$ 0.53	$ 0.49	$ 0.51	$ 0.57	$ 0.45	$ 0.53	$ 0.44	$ 2.18	$ 1.99	$ 2.46
Common stock equivalents excluded from income per diluted share because their effect would have been anti-dilutive									4	4	17