Acquisitions and Divestitures - Acquisitions (Details) (USD $) In Millions, unless otherwise specified			0 Months Ended	3 Months Ended		6 Months Ended		0 Months Ended
	Mar. 31, 2013	Dec. 31, 2011	Sep. 07, 2012 Ratalix [Member]	Mar. 31, 2013 Ratalix [Member]	Mar. 31, 2012 Ratalix [Member]	Mar. 31, 2013 Ratalix [Member]	Feb. 06, 2013 Ratalix [Member]	Feb. 06, 2013 Reseller Network [Member] Ratalix [Member]		Feb. 06, 2013 Patented Technology [Member] Ratalix [Member]		Feb. 06, 2013 Trademarks [Member] Ratalix [Member]		Dec. 31, 2012 Senior Unsecured Notes [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred Including Amounts To Be Recognized As Compensation Expense							$ 791
Business Combination, Acquisition Related Costs				6		9
Gross Carrying Amount	628	416					205	121		74		10
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life								20 years	[1]	5 years	[1]	6 years	[1]
Business Acquisition, Purchase Price Allocation, Current Assets, Cash and Cash Equivalents							127
Business Acquisition, Purchase Price Allocation, Current Assets, Receivables							112
Business Acqusition, Purchase Price Allocation, Other Tangible Assets							57
Business Acquisition, Purchase Price Allocation, Liabilities Assumed							(114)
Business Acquisition, Purchase Price Allocation, Amortizable Intangible Assets							205
Business Acquisition, Purchase Price Allocation, Deferred Taxes Asset (Liability), Net, Noncurrent							(43)
Business Combination, Consideration Transferred	16						788
Future Compensation Expense Associated with Acquisition							3
Business Acquisition, Purchase Price Allocation, Goodwill Amount	10						444
Business Acquisition, Purchase Price Allocation, Goodwill, Expected Tax Deductible Amount	7						20
Business Acquisition, Pro Forma Information [Abstract]
Revenue				1,430	1,310
Net income attributable to NCR				$ 58	$ 45
Future Compensation Expense Associated with Acquisition, Period for Recognition			3 years
Debt Instrument, Interest Rate, Stated Percentage														4.625%

[1] (1)Determination of the weighted average amortization period of the individual categories of intangible assets was based on the nature of the applicable intangible asset and the expected future cash flows to be derived from the intangible asset. Amortization of intangible assets with definite lives is recognized over the period of time the assets are expected to contribute to future cash flows.