Earnings Per Share - Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator
Income (loss) from continuing operations	$ 88	$ (143)		$ 125	$ (88)
Preferred Stock Dividends Income Statement Impact Included in Diluted Earnings Per Share From Continuing Operations	0
Preferred Stock Dividends, Income Statement Impact	12	12		25	24
Income from continuing operations attributable to NCR common stockholders	88	(155)		100	(112)
Loss from discontinued operations, net of tax	0	(2)		0	(37)
Net income attributable to NCR common stockholders	$ 88	$ (157)		$ 100	$ (149)
Weighted average outstanding shares of common stock (in shares)	120.2	117.9		119.8	118.6
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Preferred Stock	29.6		0.0	0.0
Dilutive effect of restricted stock units (in shares)	2.9	0.0		3.2	0.0
Denominator (in shares)	152.7	117.9		123.0	118.6
Diluted earnings per share:
From continuing operations (in dollars per share)	$ 0.58	$ (1.31)		$ 0.81	$ (0.94)
From discontinued operations (in dollars per share)	0	(0.02)		0	(0.32)
Total diluted earnings (loss) per share (in dollars per share)	$ 0.58	$ (1.33)		$ 0.81	$ (1.26)
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)		28.1		29.4	27.9
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)	4.7	2.3		5.1	2.3