Earnings Per Share - Basic 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
Dividends on convertible preferred stock	(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
Denominator
Weighted average outstanding shares of common stock (in shares)	119.3	119.2
Basic earnings per share:
From continuing operations (in dollars per share)	$ 0.20	$ 0.36
From discontinued operations (in dollars per share)	0	(0.29)
Total basic earnings (loss) per share (in dollars per share)	$ 0.20	$ 0.07