Earnings Per Share - Basic Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Income from continuing operations	$ 55.0	$ 57.0
Series A convertible preferred stock dividends	(12.0)	(12.0)
Deemed dividend on modification of Series A Convertible Preferred Stock	0.0	(4.0)
Deemed dividend on preferred stock redemption	0.0	(58.0)
Net Income (Loss) from Continuing Operations Available to Common Shareholders, Basic	43.0	(17.0)
Loss from discontinued operations, net of tax	(35.0)	0.0
Net income (loss) attributable to NCR common stockholders	$ 8.0	$ (17.0)
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Weighted average outstanding shares of common stock (in shares)	119.2	122.8
Earnings Per Share, Basic [Abstract]
Basic earnings from continuing operations (in dollars per share)	$ 0.36	$ (0.14)
Basic earnings from discontinued operations (in dollars per share)	(0.29)	0.00
Basic (in dollars per share)	$ 0.07	$ (0.14)