CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 27.6	$ (144.2)	$ 50.1	$ (85.6)
Other comprehensive (loss) income:
Foreign currency translation adjustments	(76.2)	24.1	(59.9)	50.6
Amortization of cash flow hedge into income, net of tax expense ($0.1 and $0.2, and $0.2 and $0.3) for the three and six months ended June 30, 2018 and 2017, respectively)	0.4	0.2	0.5	0.5
Change in fair value of cash flow hedge, net of tax expense ($0.0 and $0.1, and $0.0 and $0.1 for the three and six months ended June 30, 2018 and 2017, respectively)		0.2		0.2
Total other comprehensive (loss) income	(75.8)	24.5	(59.4)	51.3
Comprehensive loss	(48.2)	(119.7)	(9.3)	(34.3)
Less: comprehensive (loss) income attributable to noncontrolling interests	(0.8)		(0.7)	0.7
Comprehensive loss attributable to Stericycle, Inc. common shareholders	$ (47.4)	$ (119.7)	$ (8.6)	$ (35.0)