Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Segment Information
Pre-tax income	$ 5,027	$ 4,677	$ 13,729	$ 12,767	[1]
Total revenue	26,157	24,271	77,430	70,852	[1]
Total segments
Segment Information
External revenue	25,974	24,072	76,866	70,253
Internal revenue	1,989	1,917	6,148	5,627
Total revenue, reportable segments	27,963	25,990	83,015	75,880
Pre-tax income	5,484	4,968	15,118	13,514
Revenue year-to-year change (as a percent)	7.60%		9.40%
Pre-tax income year-to-year change (as a percent)	10.40%		11.90%
Pre-tax income margin (as a percent)	19.60%	19.10%	18.20%	17.80%
Global Technology Services
Segment Information
External revenue	10,322	9,496	30,427	28,036
Internal revenue	316	362	943	1,014
Total revenue, reportable segments	10,638	9,857	31,370	29,050
Pre-tax income	1,695	1,506	4,353	3,863
Revenue year-to-year change (as a percent)	7.90%		8.00%
Pre-tax income year-to-year change (as a percent)	12.50%		12.70%
Pre-tax income margin (as a percent)	15.90%	15.30%	13.90%	13.30%
Global Business Services
Segment Information
External revenue	4,832	4,572	14,407	13,465
Internal revenue	199	199	604	599
Total revenue, reportable segments	5,031	4,771	15,012	14,064
Pre-tax income	775	687	2,166	1,811
Revenue year-to-year change (as a percent)	5.50%		6.70%
Pre-tax income year-to-year change (as a percent)	12.80%		19.60%
Pre-tax income margin (as a percent)	15.40%	14.40%	14.40%	12.90%
Software
Segment Information
External revenue	5,817	5,151	17,295	15,447
Internal revenue	804	728	2,425	2,176
Total revenue, reportable segments	6,621	5,879	19,720	17,623
Pre-tax income	2,214	1,978	6,260	6,167
Revenue year-to-year change (as a percent)	12.60%		11.90%
Pre-tax income year-to-year change (as a percent)	12.00%		1.50%
Pre-tax income margin (as a percent)	33.40%	33.60%	31.70%	35.00%
Systems and Technology
Segment Information
External revenue	4,482	4,325	13,182	11,696
Internal revenue	190	196	652	572
Total revenue, reportable segments	4,672	4,521	13,834	12,267
Pre-tax income	318	295	843	283
Revenue year-to-year change (as a percent)	3.30%		12.80%
Pre-tax income year-to-year change (as a percent)	7.80%		197.90%
Pre-tax income margin (as a percent)	6.80%	6.50%	6.10%	2.30%
Global Financing
Segment Information
External revenue	520	529	1,555	1,610
Internal revenue	480	432	1,524	1,267
Total revenue, reportable segments	999	961	3,078	2,877
Pre-tax income	481	502	1,497	1,391
Revenue year-to-year change (as a percent)	4.00%		7.00%
Pre-tax income year-to-year change (as a percent)	(4.00%)		7.60%
Pre-tax income margin (as a percent)	48.20%	52.20%	48.60%	48.30%
Eliminations/other
Segment Information
External revenue	(1,806)	(1,718)	(5,585)	(5,028)
Pre-tax income	(306)	(256)	(918)	(662)
Not allocated to segments
Segment Information
Amortization of acquired intangible assets	(158)	(127)	(476)	(355)
Acquisition related charges	(21)	(13)	(32)	(23)
Non-operating retirement-related costs	$ 29	$ 104	$ 37	$ 293

[1] Amounts may not add due to rounding.