Earnings Per Share - Basic 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	Jun. 30, 2019	Jun. 30, 2018
Numerator
Income (loss) from continuing operations	$ 88	$ (143)	$ 125	$ (88)
Dividends on convertible preferred stock	(12)	(12)	(25)	(24)
Income from continuing operations attributable to NCR common stockholders	76	(155)	100	(112)
Loss from discontinued operations, net of tax	0	(2)	0	(37)
Net income (loss) attributable to NCR common stockholders	$ 76	$ (157)	$ 100	$ (149)
Denominator
Weighted average outstanding shares of common stock (in shares)	120.2	117.9	119.8	118.6
Basic earnings per share:
From continuing operations (in dollars per share)	$ 0.63	$ (1.31)	$ 0.83	$ (0.94)
From discontinued operations (in dollars per share)	0	(0.02)	0	(0.32)
Total basic earnings (loss) per share (in dollars per share)	$ 0.63	$ (1.33)	$ 0.83	$ (1.26)