Earnings Per Share - Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator
Income from continuing operations	$ 37	$ 55
Series A Convertible Preferred Stock dividends	(13)	(12)
Income from continuing operations attributable to NCR common stockholders	24	43
Loss from discontinued operations, net of tax	0	(35)
Net income attributable to NCR common stockholders	$ 24	$ 8
Weighted average outstanding shares of common stock (in shares)	119.3	119.2
Dilutive effect of restricted stock units (in shares)	2.9	4.6
Denominator (in shares)	122.2	123.8
Diluted earnings per share:
From continuing operations (in dollars per share)	$ 0.20	$ 0.35
From discontinued operations (in dollars per share)	0	(0.29)
Total diluted earnings (loss) per share (in dollars per share)	$ 0.20	$ 0.06
Series A Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from diluted per share count (in shares)	29.2	27.7
Restricted Stock Units (RSUs) and Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from diluted per share count (in shares)	4.5	1.4