Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010		Jun. 30, 2011	Jun. 30, 2010
Segment Information
Pre-tax income	$ 4,885	$ 4,575		$ 8,702	$ 8,090
Total revenue	26,666	23,724	[1]	51,273	46,581
Total segments
Segment Information
External revenue	26,476	23,523		50,892	46,181
Internal revenue	2,082	1,852		4,160	3,710
Total revenue, reportable segments	28,558	25,376		55,052	49,891
Pre-tax income	5,370	4,786		9,634	8,546
Revenue year-to-year change (as a percent)	12.50%			10.30%
Pre-tax income year-to-year change (as a percent)	12.20%			12.70%
Pre-tax income margin (as a percent)	18.80%	18.90%		17.50%	17.10%
Global Technology Services
Segment Information
External revenue	10,241	9,234		20,104	18,540
Internal revenue	320	332		627	652
Total revenue, reportable segments	10,561	9,566		20,732	19,192
Pre-tax income	1,420	1,399		2,658	2,357
Revenue year-to-year change (as a percent)	10.40%			8.00%
Pre-tax income year-to-year change (as a percent)	1.50%			12.80%
Pre-tax income margin (as a percent)	13.40%	14.60%		12.80%	12.30%
Global Business Services And Software
Segment Information
External revenue	4,866	4,483		9,575	8,893
Internal revenue	205	197		405	400
Total revenue, reportable segments	5,071	4,680		9,980	9,293
Pre-tax income	750	678		1,390	1,124
Revenue year-to-year change (as a percent)	8.30%			7.40%
Pre-tax income year-to-year change (as a percent)	10.70%			23.70%
Pre-tax income margin (as a percent)	14.80%	14.50%		13.90%	12.10%
Software
Segment Information
External revenue	6,169	5,277		11,478	10,296
Internal revenue	792	690		1,621	1,448
Total revenue, reportable segments	6,961	5,967		13,099	11,743
Pre-tax income	2,310	2,062		4,045	4,189
Revenue year-to-year change (as a percent)	16.70%			11.50%
Pre-tax income year-to-year change (as a percent)	12.00%			(3.40%)
Pre-tax income margin (as a percent)	33.20%	34.50%		30.90%	35.70%
Systems and Technology
Segment Information
External revenue	4,681	3,985		8,700	7,370
Internal revenue	218	202		462	376
Total revenue, reportable segments	4,899	4,187		9,162	7,746
Pre-tax income	393	185		525	(12)
Revenue year-to-year change (as a percent)	17.00%			18.30%
Pre-tax income year-to-year change (as a percent)	112.10%
Pre-tax income margin (as a percent)	8.00%	4.40%		5.70%	(0.20%)
Global Financing
Segment Information
External revenue	519	544		1,035	1,081
Internal revenue	547	431		1,044	834
Total revenue, reportable segments	1,066	975		2,079	1,916
Pre-tax income	496	462		1,015	889
Revenue year-to-year change (as a percent)	9.30%			8.50%
Pre-tax income year-to-year change (as a percent)	7.40%			14.20%
Pre-tax income margin (as a percent)	46.50%	47.30%		48.80%	46.40%
Eliminations/other
Segment Information
External revenue	(1,891)	(1,652)		(3,779)	(3,310)
Pre-tax income	(334)	(202)		(612)	(406)
Not allocated to segments
Segment Information
Amortization of acquired intangible assets	(159)	(114)		(318)	(229)
Acquisition related charges	(4)	(9)		(11)	(10)
Non-operating retirement-related costs	$ 12	$ 113		$ 8	$ 189

[1] Amounts may not add due to rounding.