(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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net loss attributable to Stericycle, Inc. common shareholders	$ (81.2)	$ (59.2)	$ (105.8)	$ (127.5)
Denominator:
Denominator for basic loss per share - weighted average shares (in shares)	91.5	91.1	91.4	91.0
Effect of dilutive securities:
Diluted (in shares)	91.5	91.1	91.4	91.0
Loss per share - Basic (in dollars per share)	$ (0.89)	$ (0.65)	$ (1.16)	$ (1.40)
Loss per share - Diluted (in dollars per share)	$ (0.89)	$ (0.65)	$ (1.16)	$ (1.40)