EARNINGS (LOSS) PER COMMON SHARE - Computation of Basic and Diluted Net Income (Loss) Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net income (loss) attributable to Stericycle, Inc.	$ 27.7	$ (144.0)	$ 50.2	$ (85.8)
Mandatory convertible preferred stock dividend	(8.3)	(9.2)	(17.1)	(18.6)
Gain on repurchase of preferred stock	7.2	4.4	14.5	9.0
Net income (loss) attributable to Stericycle, Inc. common shareholders	$ 26.6	$ (148.8)	$ 47.6	$ (95.4)
Denominator:
Denominator for basic earnings (loss) per share - weighted average shares (in shares)	85.6	85.3	85.6	85.2
Effect of dilutive securities:
Stock-based compensation awards	0.2	0.0	0.2	0.0
Mandatory convertible preferred stock (in shares)	0.0	0.0	0.0	0.0
Denominator for diluted earnings (loss) per share - adjusted weighted average shares and after assumed exercises (in shares)	85.8	85.3	85.8	85.2
Earnings (loss) per share - Basic (in dollars per share)	$ 0.31	$ (1.74)	$ 0.56	$ (1.12)
Earnings (loss) per share - Diluted (in dollars per share)	$ 0.31	$ (1.74)	$ 0.55	$ (1.12)