Segments (Details 1) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Information
Revenue	$ 19,280	$ 22,397	$ 59,682	$ 68,680
Pre-tax income/(loss) from continuing operations	3,621	4,361	10,846	12,891
Total Segments
Segment Information
Revenue	19,219	22,305	59,520	68,387
Global Technology Services
Segment Information
Revenue	7,937	8,837	23,891	26,696
Global Business Services
Segment Information
Revenue	4,206	4,840	12,869	14,742
Software
Segment Information
Revenue	5,136	5,708	16,165	17,857
Systems Hardware
Segment Information
Revenue	1,492	2,434	5,209	7,590
Global Financing
Segment Information
Revenue	447	487	1,386	1,502
Business Segments | Total Segments
Segment Information
Revenue	21,019	24,334	65,203	74,635
Pre-tax income/(loss) from continuing operations	$ 4,384	$ 5,195	$ 13,494	$ 15,386
Revenue year-to-year change (as a percent)	(13.60%)		(12.60%)
Pre-tax income year-to-year change (as a percent)	(15.60%)		(12.30%)
Pre-tax income margin (as a percent)	20.90%	21.30%	20.70%	20.60%
Business Segments | Global Technology Services
Segment Information
Revenue	$ 8,127	$ 9,089	$ 24,480	$ 27,435
Pre-tax income/(loss) from continuing operations	$ 1,274	$ 1,625	$ 3,516	$ 4,509
Revenue year-to-year change (as a percent)	(10.60%)		(10.80%)
Pre-tax income year-to-year change (as a percent)	(21.60%)		(22.00%)
Pre-tax income margin (as a percent)	15.70%	17.90%	14.40%	16.40%
Business Segments | Global Business Services
Segment Information
Revenue	$ 4,326	$ 4,975	$ 13,249	$ 15,158
Pre-tax income/(loss) from continuing operations	$ 673	$ 861	$ 1,926	$ 2,633
Revenue year-to-year change (as a percent)	(13.00%)		(12.60%)
Pre-tax income year-to-year change (as a percent)	(21.80%)		(26.80%)
Pre-tax income margin (as a percent)	15.60%	17.30%	14.50%	17.40%
Business Segments | Software
Segment Information
Revenue	$ 5,921	$ 6,570	$ 18,684	$ 20,508
Pre-tax income/(loss) from continuing operations	$ 1,899	$ 2,333	$ 6,107	$ 6,935
Revenue year-to-year change (as a percent)	(9.90%)		(8.90%)
Pre-tax income year-to-year change (as a percent)	(18.60%)		(11.90%)
Pre-tax income margin (as a percent)	32.10%	35.50%	32.70%	33.80%
Business Segments | Systems Hardware
Segment Information
Revenue	$ 1,613	$ 2,616	$ 5,529	$ 8,131
Pre-tax income/(loss) from continuing operations	$ (24)	$ (99)	$ 255	$ (354)
Revenue year-to-year change (as a percent)	(38.30%)		(32.00%)
Pre-tax income year-to-year change (as a percent)	(75.60%)
Pre-tax income margin (as a percent)	(1.50%)	(3.80%)	4.60%	(4.40%)
Business Segments | Global Financing
Segment Information
Revenue	$ 1,031	$ 1,084	$ 3,261	$ 3,403
Pre-tax income/(loss) from continuing operations	$ 562	$ 475	$ 1,690	$ 1,664
Revenue year-to-year change (as a percent)	(4.90%)		(4.20%)
Pre-tax income year-to-year change (as a percent)	18.10%		1.60%
Pre-tax income margin (as a percent)	54.50%	43.90%	51.80%	48.90%
Internal transactions
Segment Information
Pre-tax income/(loss) from continuing operations	$ (380)	$ (402)	$ (1,294)	$ (1,433)
Internal transactions | Total Segments
Segment Information
Revenue	(1,800)	(2,029)	(5,683)	(6,248)
Internal transactions | Global Technology Services
Segment Information
Revenue	(190)	(252)	(589)	(739)
Internal transactions | Global Business Services
Segment Information
Revenue	(120)	(135)	(380)	(416)
Internal transactions | Software
Segment Information
Revenue	(785)	(862)	(2,519)	(2,652)
Internal transactions | Systems Hardware
Segment Information
Revenue	(121)	(182)	(320)	(541)
Internal transactions | Global Financing
Segment Information
Revenue	$ (584)	$ (598)	$ (1,874)	$ (1,900)