Earnings Per Share - Computation of Earnings Per Common Share Attributable to Unisys Corporation (Detail) - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Basic earnings (loss) per common share computation:
Net income (loss) attributable to Unisys Corporation	$ (13,200,000)	$ 6,100,000	$ (6,400,000)	$ 50,500,000
Weighted average shares (in shares)	58,245	51,021	53,815	50,918
Basic earnings (loss) per common share (in dollars per share)	$ (0.23)	$ 0.12	$ (0.12)	$ 0.99
Diluted earnings (loss) per common share computation:
Net income (loss) attributable to Unisys Corporation	$ (13,200,000)	$ 6,100,000	$ (6,400,000)	$ 50,500,000
Add interest expense on convertible senior notes, net of tax of zero	0	0	0	14,600,000
Interest expense on convertible senior notes, tax	0	0	0	0
Net income (loss) attributable to Unisys Corporation for diluted earnings per share	$ (13,200,000)	$ 6,100,000	$ (6,400,000)	$ 65,100,000
Weighted average shares (in shares)	58,245	51,021	53,815	50,918
Plus incremental shares from assumed conversions:
Employee stock plans (in shares)	0	697	0	479
Convertible senior notes (in shares)	0	0	0	21,868
Adjusted weighted average shares (in shares)	58,245	51,718	53,815	73,265
Diluted earnings (loss) per common share (in dollars per share)	$ (0.23)	$ 0.12	$ (0.12)	$ 0.89
Stock options and restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive weighted average securities (in shares)	1,462	1,136	1,394	1,274
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)	13,951	21,868	19,229	0
Convertible senior notes interest rate	5.50%		5.50%