(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
	Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net (loss) income attributable to Stericycle, Inc.	$ (37.8)	$ 22.5
Mandatory convertible preferred stock dividend		(8.8)
Gain on repurchases of preferred stock		7.3
Net (loss) income attributable to Stericycle, Inc. common shareholders	$ (37.8)	$ 21.0
Denominator:
Denominator for basic (loss) earnings per share - weighted average shares (in shares)	90.7	85.5
Effect of dilutive securities:
Stock-based compensation awards		0.3
Denominator for diluted earnings (loss) per share - adjusted weighted average shares and after assumed exercises (in shares)	90.7	85.8
(Loss) earnings per share – Basic (in dollars per share)	$ (0.42)	$ 0.25
(Loss) earnings per share – Diluted (in dollars per share)	$ (0.42)	$ 0.25