(LOSS) EARNINGS PER COMMON SHARE - Computation of Basic and Diluted Loss Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net loss attributable to Stericycle, Inc.	$ (20.1)	$ (37.8)
Net loss attributable to Stericycle, Inc. common shareholders	$ (20.1)	$ (37.8)
Denominator:
Denominator for basic loss per share - weighted average shares (in shares)	91.3	90.7
Effect of dilutive securities:
Denominator for diluted (loss) earnings per share - adjusted weighted average shares and after assumed exercises	91.3	90.7
(Loss) earnings per share - Basic (in dollars per share)	$ (0.22)	$ (0.42)
(Loss) earnings per share - Diluted (in dollars per share)	$ (0.22)	$ (0.42)