Earnings Per Share - Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Income (loss) from continuing operations	$ 85	$ 118	$ (3)	$ 272
Preferred Stock Dividends Income Statement Impact Included in Diluted Earnings Per Share From Continuing Operations	0	0	(36)	(36)
Deemed dividend on modification of Series A convertible preferred stock	0	0	0	(4)
Deemed dividend on Series A convertible preferred stock related to redemption	0	0	0	(58)
Net Income (Loss) from Continuing Operations Available to Common Shareholders, Diluted	85	118	(39)	174
(Loss) income from discontinued operations, net of tax	(1)	0	(38)	5
Net loss attributable to NCR common stockholders	$ 84	$ 118	$ (77)	$ 179
Weighted Average Number of Shares Outstanding, Basic	118.0	121.5	118.4	121.9
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Preferred Stock	28.4	26.9	0.0	0.0
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	2.9	4.7	0.0	5.0
Diluted (in shares)	149.3	153.1	118.4	126.9
Income (Loss) from Continuing Operations, Per Diluted Share	$ 0.57	$ 0.77	$ (0.33)	$ 1.37
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	(0.01)	0.00	(0.32)	0.04
Earnings Per Share, Diluted	$ 0.56	$ 0.77	$ (0.65)	$ 1.41
Series A Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			28.1	27.5
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	3.0	0.8	6.7	0.8