Quarterly Information (unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 1,638	$ 1,401	$ 1,310	$ 1,094	$ 1,403	$ 1,205	$ 1,175	$ 1,027	$ 5,443	$ 4,810	$ 4,599
Gross margin	363	292	270	210	286	247	241	190
Operating income (loss)	(10)	18	49	8	54	36	33	(17)	65	106	103
Income (loss) from continuing operations, net of tax									49	119	65
Income (loss) from discontinued operations, net of tax	4	0	(3)	2	6	4	9	(1)	3	18	(95)
Net income (loss) attributable to noncontrolling interests	(3)	(1)	2	1	(1)	2	0	2	(1)	3	3
Net income (loss) attributable to NCR	(9)	16	33	13	39	83	31	(19)	53	134	(33)
Net (loss) income per common share from continuing operations
Basic	$ (0.08)	$ 0.1	$ 0.23	$ 0.07	$ 0.2	$ 0.49	$ 0.14	$ (0.11)	$ 0.32	$ 0.73	$ 0.39
Diluted	$ (0.08)	$ 0.1	$ 0.22	$ 0.07	$ 0.2	$ 0.49	$ 0.14	$ (0.11)	$ 0.31	$ 0.72	$ 0.39
Net income (loss) per common share
Basic	$ (0.06)	$ 0.1	$ 0.21	$ 0.08	$ 0.24	$ 0.52	$ 0.19	$ (0.12)	$ 0.34	$ 0.84	$ (0.21)
Diluted	$ (0.06)	$ 0.1	$ 0.21	$ 0.08	$ 0.24	$ 0.51	$ 0.19	$ (0.12)	$ 0.33	$ 0.83	$ (0.21)
Impairment of long-lived and other assets									(88)	0	0
Total Losses [Member] | Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Net income (loss) per common share
Impairment of long-lived and other assets	$ (88)