Earnings Per Share - Computation of Earnings (Loss) Per Common Share Attributable to Unisys Corporation (Detail) - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Basic earnings (loss) per common share computation:
Net income (loss) attributable to Unisys Corporation	$ (19,400,000)	$ 40,600,000
Weighted average shares (in shares)	51,418	50,748
Basic earnings (loss) per common share (in dollars per share)	$ (0.38)	$ 0.80
Diluted earnings (loss) per common share computation:
Net income (loss) attributable to Unisys Corporation	$ (19,400,000)	$ 40,600,000
Add interest expense on convertible senior notes, net of tax of zero	0	4,800,000
Interest expense on convertible senior notes, tax	0	0
Net income (loss) attributable to Unisys Corporation for diluted earnings per share	$ (19,400,000)	$ 45,400,000
Weighted average shares (in shares)	51,418	50,748
Plus incremental shares from assumed conversions:
Employee stock plans (in shares)	0	327
Convertible senior notes (in shares)	0	21,868
Adjusted weighted average shares (in shares)	51,418	72,943
Diluted earnings (loss) per common share (in dollars per share)	$ (0.38)	$ 0.62
Stock options and restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive weighted average securities (in shares)	1,401	2,044
Common shares issuable upon conversion of the 5.50% convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive weighted average securities (in shares)	21,868	0
Convertible senior notes interest rate	5.50%