Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (22.5)	$ 6.7	$ (4.5)	$ 35.2
Benefit plan adjustments:
Benefit plan actuarial gains	12.4	9.2	44.2	29.5
Benefit plan prior service costs	(1.3)	(1.2)	(3.7)	(3.7)
Deferred profit sharing	0.0	(0.1)	0.0	(0.2)
Total benefit plan adjustments	11.1	8.1	40.5	26.0
Foreign currency translation adjustments	43.6	(34.9)	(48.5)	(25.2)
Gains (losses) on cash flow hedges	4.1	(3.9)	(13.2)	(22.4)
Other comprehensive income (loss) before tax	58.8	(30.7)	(21.2)	(21.6)
Provision for income taxes	4.1	0.7	6.3	0.5
Other comprehensive income (loss)	54.7	(31.4)	(27.5)	(22.1)
Comprehensive income (loss)	32.2	(24.7)	(32.0)	13.1
Less comprehensive income attributable to noncontrolling interests	3.4	1.6	7.3	4.3
Comprehensive income (loss) attributable to Brink's	$ 28.8	$ (26.3)	$ (39.3)	$ 8.8