Loss Per Share - Computation of Earnings (Loss) Per Common Share Attributable to Unisys Corporation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Basic loss per common share computation:
Net loss attributable to Unisys Corporation	$ (57.3)	$ (157.8)
Weighted average shares (in shares)	67,387	64,423
Basic loss per common share (in dollars per share)	$ (0.85)	$ (2.45)
Diluted loss per common share computation:
Net loss attributable to Unisys Corporation	$ (57.3)	$ (157.8)
Weighted average shares (in shares)	67,387	64,423
Plus incremental shares from assumed conversions of employee stock plans (in shares)	0	0
Adjusted weighted average shares (in shares)	67,387	64,423
Diluted loss per common share (in dollars per share)	$ (0.85)	$ (2.45)
Stock options and restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive weighted average securities (in shares)	837	1,067