Earnings Per Share - Computation of Loss Per Common Share Attributable to Unisys Corporation (Detail) - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Basic earnings (loss) per common share computation:
Net income (loss) attributable to Unisys Corporation	$ (42,000,000)	$ 21,600,000	$ (74,700,000)	$ (18,300,000)
Weighted average shares (in shares)	50,437	50,069	50,346	50,036
Basic earnings (loss) per common share (in dollars per share)	$ (0.83)	$ 0.43	$ (1.48)	$ (0.37)
Diluted earnings (loss) per common share computation:
Net income (loss) attributable to Unisys Corporation	$ (42,000,000)	$ 21,600,000	$ (74,700,000)	$ (18,300,000)
Add interest expense on convertible notes, net of tax of zero	0	4,500,000	0	0
Interest expense on convertible notes, tax	0	0	0	0
Net income (loss) attributable to Unisys Corporation for diluted earnings per share	$ (42,000,000)	$ 26,100,000	$ (74,700,000)	$ (18,300,000)
Weighted average shares (in shares)	50,437	50,069	50,346	50,036
Plus incremental shares from assumed conversions:
Employee stock plans (in shares)	0	167	0	0
Convertible notes (in shares)	0	21,550	0	0
Adjusted weighted average shares (in shares)	50,437	71,786	50,346	50,036
Diluted earnings (loss) per common share (in dollars per share)	$ (0.83)	$ 0.36	$ (1.48)	$ (0.37)