Segments: (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Information
Revenue	$ 24,364	$ 24,924	$ 46,848	$ 48,332
Pre-tax income	5,171	4,144	8,151	7,750
Global Technology Services
Segment Information
Revenue	9,414	9,536	18,744	19,140
Global Business Services
Segment Information
Revenue	4,534	4,606	9,017	9,091
Software
Segment Information
Revenue	6,488	6,423	12,149	11,995
Systems and Technology
Segment Information
Revenue	3,331	3,758	5,722	6,864
Global Financing
Segment Information
Revenue	504	487	1,016	985
Total Segments
Segment Information
Revenue	24,271	24,809	46,648	48,075
Business Segments
Segment Information
Revenue	26,390	26,737	50,866	51,922
Pre-tax income	5,983	4,989	9,812	9,425
Business Segments | Global Technology Services
Segment Information
Revenue	9,661	9,828	19,232	19,680
Pre-tax income	1,850	1,514	3,196	3,099
Revenue year-to-year change (as a percent)	(1.70%)		(2.30%)
Pre-tax income year-to-year change (as a percent)	22.20%		3.10%
Pre-tax income margin (as a percent)	19.20%	15.40%	16.60%	15.70%
Business Segments | Global Business Services
Segment Information
Revenue	4,674	4,795	9,298	9,459
Pre-tax income	832	623	1,461	1,326
Revenue year-to-year change (as a percent)	(2.50%)		(1.70%)
Pre-tax income year-to-year change (as a percent)	33.70%		10.20%
Pre-tax income margin (as a percent)	17.80%	13.00%	15.70%	14.00%
Business Segments | Software
Segment Information
Revenue	7,345	7,161	13,939	13,563
Pre-tax income	2,683	2,443	4,601	4,457
Revenue year-to-year change (as a percent)	2.60%		2.80%
Pre-tax income year-to-year change (as a percent)	9.80%		3.20%
Pre-tax income margin (as a percent)	36.50%	34.10%	33.00%	32.90%
Business Segments | Systems and Technology
Segment Information
Revenue	3,521	3,893	6,080	7,118
Pre-tax income	25	(141)	(635)	(546)
Revenue year-to-year change (as a percent)	(9.50%)		(14.60%)
Pre-tax income year-to-year change (as a percent)	117.90%		16.30%
Pre-tax income margin (as a percent)	0.70%	(3.60%)	(10.40%)	(7.70%)
Business Segments | Global Financing
Segment Information
Revenue	1,189	1,061	2,318	2,101
Pre-tax income	593	550	1,188	1,088
Revenue year-to-year change (as a percent)	12.00%		10.30%
Pre-tax income year-to-year change (as a percent)	7.70%		9.20%
Pre-tax income margin (as a percent)	49.80%	51.80%	51.30%	51.80%
Business Segments | Total Segments
Segment Information
Revenue	26,390	26,737	50,866	51,922
Pre-tax income	5,983	4,989	9,812	9,425
Revenue year-to-year change (as a percent)	(1.30%)		(2.00%)
Pre-tax income year-to-year change (as a percent)	19.90%		4.10%
Pre-tax income margin (as a percent)	22.70%	18.70%	19.30%	18.20%
Internal transactions
Segment Information
Revenue	(2,119)	(1,928)	(4,218)	(3,847)
Pre-tax income	(507)	(379)	(1,031)	(718)
Internal transactions | Global Technology Services
Segment Information
Revenue	(247)	(292)	(488)	(540)
Internal transactions | Global Business Services
Segment Information
Revenue	(140)	(188)	(281)	(368)
Internal transactions | Software
Segment Information
Revenue	(857)	(738)	(1,789)	(1,569)
Internal transactions | Systems and Technology
Segment Information
Revenue	(190)	(135)	(358)	(255)
Internal transactions | Global Financing
Segment Information
Revenue	(685)	(575)	(1,303)	(1,116)
Internal transactions | Total Segments
Segment Information
Revenue	$ (2,119)	$ (1,928)	$ (4,218)	$ (3,847)