(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		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net loss attributable to Stericycle, Inc. common shareholders	$ (4.5)	$ (30.5)	$ (24.6)	$ (68.3)
Net loss attributable to Stericycle, Inc. common shareholders	$ (4.5)	$ (30.5)	$ (24.6)	$ (68.3)
Denominator:
Denominator for basic loss per share - weighted average shares (in shares)	91.4	91.0	91.4	90.9
Effect of dilutive securities:
Diluted	91.4	91.0	91.4	90.9
(Loss) earnings per share - Basic (in dollars per share)	$ (0.05)	$ (0.33)	$ (0.27)	$ (0.75)
(Loss) earnings per share - Diluted (in dollars per share)	$ (0.05)	$ (0.33)	$ (0.27)	$ (0.75)