(LOSS) EARNINGS PER COMMON SHARE - Computation of Basic and Diluted (Loss) Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net (loss) income attributable to Stericycle, Inc.	$ (30.5)	$ 27.7	$ (68.3)	$ 50.2
Mandatory convertible preferred stock dividend		(8.3)		(17.1)
Gain on repurchases of preferred stock		7.2		14.5
Net (loss) income attributable to Stericycle, Inc. common shareholders	$ (30.5)	$ 26.6	$ (68.3)	$ 47.6
Denominator:
Denominator for basic (loss) earnings per share - weighted average shares (in shares)	91.0	85.6	90.9	85.6
Effect of dilutive securities:
Stock-based compensation awards		0.2		0.2
Denominator for diluted (loss) earnings per share - adjusted weighted average shares and after assumed exercises	91.0	85.8	90.9	85.8
(Loss) earnings per share - Basic (in dollars per share)	$ (0.33)	$ 0.31	$ (0.75)	$ 0.56
(Loss) earnings per share - Diluted (in dollars per share)	$ (0.33)	$ 0.31	$ (0.75)	$ 0.55